When building houses, I tend to use Maxis content only because we all have our favourite custom content. I put great emphasis on the playability of the lots to keep the simmies happy. I suppose I just can't stand seeing the simmies stomp their feet in anger...
Being a story writer, I'm still a big fan of TS2. (We do have also TS3 in the household but, however, I'm not playing. The looks of the pudding faced sims simply don't appeal to me at all).
Having downloaded a considerable amount of custom stuff from MTS, I've decided to start contributing something myself. I've only just begun but there's more to come.
You may use my stuff in your game as you please and have them in your stories, if you like. No problem. I don't care as long as you don't upload to another site and claim as your own.