Is there a way to set different tracks with different time signatures and be able to choose from which track's metronome to hear during playback and recording? If not, what's the next best thing?

You can set up different metronome tracks pretty easily, but you're going to have to have one main time signature. By the nature of (good) polyrhythmic music this shouldn't be a problem anyway except when it comes to creating the parts. I would recommend just setting the project Timebase to time so that it doesn't screw up your project when you switch time signatures intentionally just to edit particular items. It's messy. But so is the the whole musical idea of poly rhythm you cant realy expect a DAW to represent it in a logical way. The best answer is to tailor it to your project. If you are going to be doing mostly percussion programming in MIDI in various time sigs, make that your focus and whatever is the most dominant time signature at any point, work around that.

Thanks for the reply! I'll try that out.

you could use another project tab just for metronome playback - set the tab to "run background projects" & "synchronise play start times..." and then you can have a different time sig / metronome playing at the same time as your track.

Related: (post #5)

I've been through this already; Fergler's reply is spot on.