I finally had a chance to look at what you uploaded, and it's all minor stuff. Your neck seam is fine, and no tone differences at that waist seam. This tells me it's bone weight, morphs, or the rare mesh issue. I redid both bones and morphs using a bra .wso. Seam still visible, so the mesh got buggered at some point. Imported it to Blender, along with a clean bra mesh. I removed both arms, and the bottom row of faces at the waist, and replaced them with same from the bra mesh. Then, merged vertices, fixed sharp edges, set normals average corner angle and exported as object.

I generally work with objects, because I find they give me a cleaner mesh. If geom works for you, it can cut out a few steps of conversions.

Now, I used the whole arms, because I wasn't concerned with sleeve overlap. BUT, in the UV, I selected the vertices above the elbow to shoulder, shrunk them on Y axis a bit then moved them down on Y to space out similar to the next rows of vertices. I use either average corner angle or average face area depending on how they look and what I'm trying to acheive. Moving the UV a little is fine, but too much and you may notice arm shading looks funny.

I converted the object to geom and added bones, using EA bra as reference. Then seam fixer which @CardinalSims mentioned. Next, convert to .wso and used my bra w/ pregnant morph as reference for morphs. Basic EA bra would do the same, but without pregnant morph. I imported back to TSRW that I generated from your package, and seam is gone.

I also found you did not generate mipmaps in your textures. I think CardinalSims covered that in one of the tutorials?

That missing face is also a minor defect. I mess up and need to fix those often! If it's not on a seam, just select 2 edges and push "F". (Blender 2.93) Fill is also in the face menu in edit mode.

And congratulation on your new project! Yes, a lot to learn, and that never seems to end.

Oh my gosh, I'll have to really go over this and study CardinalSims Blender guide too. This is a lot of helpful info thank you!

At this point I called my project a bad name in the title, just getting so frustrated lol! I'm sorry to ask another question because it's already been a lot but is there a way to view the bottom part on the model in TSRW? I have created a 2nd project with a different mesh following much of what you and CardinalSims have given, also combined with a few tutorials and I think I've managed to fix that seam at the neck thing that happens, kind of like the waste issue. Like CardinalSims said it's been having me in circles, but I think I'm at a point where I can export this 2nd project but there's no bottom and no option under Parts. If there's not an option that's okay, I'll just export and see what happens, fingers crossed.

Edit: also mipmaps? is that something like an option when exporting with the nvidia plugin? if I'm remembering correctly, perhaps not.

If you're using Photoshop + the DDS plugin, the option is here and should stay on by default once selected:

May look slightly different in various versions.

Okay thanks, In the tutorial I watched it said to uncheck it. I'll have to educate myself on what it is and check out your tutorial. Edit: Could you link me to it Plz?

I did manage to complete a mesh conversion now with no seams in waist nor neck. TSRW gave me a hard time and drove me batty. The mesh had come out with a neck line seam the first time, so I took the mesh through milkshake again and did the align vertex's on all LOD's before taking the poly down and exporting but I also imported the swimsuit reference and merged the neckline very tediously. I then used MTK seam fixer

I then opened up the TSRW and chose an upper body mesh and I believe I chose the same one the first time when it came out fine except the neck. But this time when I imported my LOD0 the bottom half of the body disappeared. I seen in CAS that my sim had no bottom as well after exporting the mesh. So I tried again. Did everything the exact same while creating the TSRW project, chose the same upper body mesh but this last time the bottom half was there after importing the LOD0. Very confusing, but I'm happy that I finally completed a conversion.

Could you link what tutorial is giving that information, if you remember which one it was? That's actually quite a harmful bit of misinformation unless they have included a good reason to do so- mipmaps reduce performance strain, something that TS3 needs as much of as it can get.
I haven't actually formally covered textures yet, but I'm happy to answer questions and provide screenshots of things I don't have in published form.

My guess for the weird behaviour would be that you accidentally used a full body outfit the first time. As these replace the upper and lower body, the legs would disappear as they aren't included in your mesh.
I do most things manually with S3PE, which is a bit more tedious / has less of a user interface, but more predictable. Though both workflows will have their fair share of user error- sometimes you just misclick, or do something in a different order, or forget a step and the end result comes out looking like you baked a shepherd's pie when you were following a recipe for a trifle

Let she who has not been frustrated, used naughty words, and swan dived into a bottle of vodka be the first to criticize you!

You said there is no bottom in TSRW? I have only had that when using a 2 group dress to make a 2 group top. IF that is the case, in the Project tab, scroll down to Clothing Type, click the + and click Upper Body. Save and reopen the file, and there will be a bottom.

If you use Photoshop, I defer to CardinalSims regarding mipmaps. If you use GIMP, it's a little different. I can help if you need, but no sense confusing things if you don't use it.

I already went thru my basic work flow. I never touch Milkshape for garments, except to sometimes convert fixed morphs from object to .wso. Blender to MTK to TSRW.

lol So much work to create a masterpiece and it comes out a buggered piece omg it's a sinking feeling but yes part of the learning, if I could just chill out and not rush myself. Okay the choosing the wrong body part makes sense now, I was very confused.

This is the link to the video tutorial and it's at around 26:57 in the timeline https://www.youtube.com/watch?v=uNSaR6xFah0 (Really sweet girl and her guide did help me kind of lift off)

LadySmoks]Let she who has not been frustrated, used naughty words, and swan dived into a bottle of vodka be the first to criticize you! Lmao! I wish sometimes but I can't drink

I realize the mipmaps are important now

For the body part, Thank you! Yes I realize that's exactly what I did.

Thank you, I've sent the creator an ask on Tumblr letting her know that step could be revised.

I also noticed in that part of the tutorial she has her Compression Effort settings on the lowest quality (Fastest instead of Highest)
If you also copied those settings, please use Highest. Fastest will leave unnecessary compression artifacts and there are no drawbacks to using the highest- the option for lower quality exists for contexts you will not encounter while modding TS3.
While I'm at it, 3-channel masks and speculars can be saved in BC1/DXT1 to optimise on texture memory. The current version of the texture tools exporter is usually pretty good at this looking indistinguishable from BC3/DXT5, but that can remain an option if you do lose wanted detail.

Well, remember what I told you about changing Clothing Type. It is a useful tool if you ever make things with alternate shaders, but also need to use simskin for exposed body parts.

Again to add to something @CardinalSims wrote... This may be something that doesn't apply to you, if you are using Photoshop, since I don't use it and don't know how textures come out from that program. In GIMP, I find dxt1 is okay for rgb masks, if they are not being used to create some level of detail or lines. Generally, if the mask uses blocks, dxt1 is ok. There are also rare times when I use uncompressed multipliers, because of certain details lost in dxt5. And yes, uncompressed does make the package a bit bigger.

TY! This info is extremely invaluable I'm excited to convert my next mesh. So many steps to remember I have to make a list of steps and settings

I really appreciate all your shared knowledge on this TY! If I ever cancel the insanely priced photoshop subscription and move to GIMP which is something I should do. I also have Paint, I do need to look up free options

For my next mesh I plan to look over this thread and take note of everything, thanks again. I appreciate yr time!

@CardinalSims and @LadySmoks
I just wanted to share the final outcome of the original mesh I was having issues with. After starting from scratch and implementing all the advice and suggestions here as well as watching another youtube video. I'm just happy to report the mesh finally came out perfect!

No seams, no weird shadows in CAS. For the neck seam I used a reference in Milkshake and used the S2unimesh to merge the vertex's with the original. I honestly don't know wth I was doing but it worked lol!.

Anyways so happy to have learned as much as I have so far and really appreciate your help