So, the mixer we use is the Soundcraft Ui24R. We all have aux-mixes off of that stage box. In a situation where there's a decent (or at least an 'independent' FOH PA, we just in sert it between the stage lines and the FOH snake. They get clean splits with nothing added/done to them to mix as they please. If we're in a room that we need to provide FOH, we just use the main mix on the Ui24R as the FOH mix. We have a 'generic' main mix that can be the starting point for every show as needed. Since the Soundcraft save all your last settings (or you can load previously saved settings if you play a room lots)...it's not really any more work if you're doing your own PA. It also has the proficiency of mix and control as something like the M32/X32 boards for FOH Mixing.
We still do have live amps on stage, but after years of gigs, they're all pretty well dialed in.
On the Drum thing...in a room that we reach where the 'house' sound says "Oh we don't really mic drums here" or even only mic one or two pieces. We have a few strategies. First off is that we can just put an overhead on the kit and just use it for the IEMs. Or if we want we can do overhead-kick or overhead-snare-kick. Though honestly kit is loud enough on stage that many nights I'm not doing more than just a little hat and kick.
Ha, I have a Ui24R and haven't used it yet! I know it's overkill, but I figured I would rather have more and not use it than want more later.

