We have an IEM rack that we built and all pitched in $$ for. In the rack, there is a splitter. The splitter takes the inputs, duplicates the signal, and splits them to two snake tails. One of the tails goes into our own mixer that we use to control our IEM mixes. The other tail goes straight to FOH.
For the guitars: I use an Axe FX and my other guitarist uses a Kemper (surprisingly, no arguments!). For my Axe, I have a patch that sends Output 1 (WITH cabinet emulation) to our splitter (which goes to FOH and IEMs) and Output 2 (WITHOUT cab emulation) to a real Marshall cab on stage. We do NOT mic up our cabs. They are purely for filling up the stage sound and blasting out eardrums in the front row. Since we've moved to this setup, we get compliments for our sound after every show, from the FOH crew and audience members.
I highly recommend getting custom molds for IEMs. They do a much better job blocking out the on-stage volume and letting you hear the mix in your ears. If you're not used to jamming with people over headphones, it may be a strange sensation for a little bit, but it is sooo much better than wearing earplugs and cranking on-stage monitors, in my opinion.