I have an H1 & H5X with 80/120/50-110 and a IQ3100. I love the back, it's the best of the 4 I've ever owned (P22+, Credo 60/80 were the others) and 100mp is plenty for all applications. For anything I need faster af for I shoot D850. Really most jobs I go to with the H kit and D850+24-70. At some point I'd like a backup back (maybe a Credo 50), but that's not happening in covid times.
I haven't shot H6X, but don't think there's much difference between the 5X and 6X (and 4X for that matter. I think the 5+6 platforms may be a bit more stable though). I've been in this system 18m, and yeah, it's frustrating I'll never be able to upgrade the back, but also, don't see much need to.
-Doug