Dave, I am here to help anyway I can. We use the Shure SE 215’s as well. All the following is based on my experience:
We found it important for everyone to use the same in-ears. The 215’s are really good for the price Even tho everyone hears differently, at least the monitor settings will send the same response to the same receivers. The Kick, and Bass are always a big “want” and I can notch out a boost on just those frequencies they need in the monitor mix. It is also very important to run a stereo monitor mix, as you can pan everything, whether in wide stereo or mono. into a place in the stereo spectrum. Much easier to hear the separate parts.
If you are blessed with multiple aux outs, and a headphone amp with multiple in’s and out’s, everyone can have their own separate mix, referred to as “more me”. As I do with one band, Guitarist is always loud and ruins our monitor mix. I put his mix thru a different stereo aux where his guitar is loudly panned to 11 and 1 o’clock. His vocals run down the middle with other voices panned elsewhere, at different positions. I also run bass and drums in different pans and to a volume he wants them to be. He is satisfied. Myself, drummer, and bassist are happy with a shared mix, where the guitar sits in the mix very well.
The headphones MUST be twisted into your ears for a tight fit where you cannot hear anything outside of them. It takes awhile to get used to them.