I had gone from a 70D to a 7DII a year ago. The focus system and FPS made it a worthwhile upgrade for wildlife and BIF that I do. As I thought I would, I missed having the flip screen. After having had a 5D classic for a time, I knew I wanted to try FF again, but something more modern. Early in the calendar year, I added a 6DII for landscape, portrait, vaca, etc, and then a 24-70is. The flip screen, WiFi, and improved AF over the 6DI were main drivers in the decision. The menu and button layout were familiar so it was an easy transition. It’s definitely NOT a mini 5D4, but more of a full frame 80D.
I’ve not encountered DR issues, but I don’t necessarily push those limits in post anyway. Yes, by all accounts the lower ISO DR is worse than the 80D. I shoot almost exclusively in raw though, so I can’t speak to how in camera jpg processing will be in one vs the other.
I’ve used the 6DII for some wildlife and BIF and have been pleasantly surprised that it’s more capable than expected. Yes the points are clustered, but I’m more of a center of the frame shooter, so it does not hinder me.
I will defer any DOF discussion to the other threads you are discussing the same topic of FF vs crop.
Early summer I was not sure if I would keep the 6DII wondering if I really needed it, and could I justify the addt’l investment. I took the 7DII on a family beach vaca to Cape Cod. Got some great pics, I wondered how thankful I’d be for weather sealing when heavy mist moved in during a boat tour, but no flip screen, no WiFi, and a couple lesser things changed my mind. I subsequently added a 16-35is and Rok14. It was great having both bodies at an airshow this summer and I’ve shot a couple corporate events for my company with the 6DII. I’ve been quite happy with it.