any supported i2c devices (just friends, txo, er-301) will work regardless of which module you’re running polyES on.
what happens with the physical outputs is up to you - it depends on how you map it. it’s completely flexible. you can map different voices to i2c and physical, you can map same voices, you can send a voice to physical output 1, er-301 port 4, just friends output 3 etc etc
re: monobright - really hard to tell. some functionality might be difficult to use with non vb.
i don’t think that’s supported, unless there is some hardware mod i’m not aware of.