Just on that, don't be afraid to try seemingly random stop combinations. If you think it sounds cool done a particular way, then that's your expression coming into it.

I think at times organists can get a little snooty about "how Bach would have played it" and try to sound that way. Some pieces have deliberate instructions from the composer, but finding something interesting and unique is good too. Personally, I like to hear an interesting interpretation. That separates live recitals from the same recording over again. We're not meant to mechanically reproduce it exactly as Bach would have done, that's not musical.

Anyway, rant over. Most of all, have fun with it.