I haven't been processing my effects, as a rule, just assigning them... but I'm trying some ideas I'm finding in tutorials... right now I'm trying to compress a clip, but all my compressors convert my signal to stereo, which I don't want, and I can't find an option that pertains to that. Do I simply need to find a mono compressor plug in? Or am I missing something?

Some plugins are mono only, and will always produce mono output. With stereo plugins I think you should get a mono clip from Process > Apply FX if the track's Interleave button is set to mono.

Processed clips within a track will end up as stereo or mono depending on whether the track's interleave is set to stereo or mono. It seems to work this way, although I have not seen any documentation about it.