I'm working on jw's glow in the dark wall base. I wanted to see if I could get semi functional black light posters out of it. They look great, but there's a slight opacity that these would be better off without. Any advice would be appreciated!

What blend modes are you using in the TXMT?

Had a look at it earlier, but couldn't se any obvious points of improvement, unless the TXMT is completely redone with other setttings (not sure if there's a different ioption for glow effect? It's not the thing I do the most of).

The "Additive" setting is used in the Blend mode to achieve the glow effect.
"None" in the Alpha setting that affects the transparency/cutout.

There are potentially a few others that can affect the alpha a bit, possibly more so in this case than if you're using a regular Blend/0 for opacity, or None/1 for cutouts setting for those two.

Using DXT5 for transparent/cutout textures, none for sharpen, and not using "update all sizes" should get you the clearest textures.
(Update sizes used with DXT can have the opposite effect - it's only useful with Import. DXT3 can be used for fully opaque textures, simple cutouts and simple transparency, while DXT5 is best for layered transparency and softer cutout lines, if you don't feel you're getting the best result with DXT3).