Dear Frank
Every day, I used a D750 for 2 months as my backup DSLR. And l also dislike the D750 shutter clack! Yet, let's say it is okay....but there are better Nikon DSLRs in the current stable.
Otherwise, I rely on the D500 (since November last year, an upgrade from the D7200). And I also use the classic Df. It's in its own league for those of us who began with the FM2 and its kin, and the F3. I have always concentrated on mainly wildlife and landscapes, but also for portraits, social events etc. Hands down, the D500 wins on AF, faster continuous shooting and the pro control layout. Overall the ergonomics of the D500 are much better to my hand. It feels more solid overall. Given the costs, the D500 wins for my needs. I recommend the grip - I'm very happy with the Meike.
For FX there's the D810 as the optimal but more costly option. And there is the awaited upgrade [D820 see sister thread currently active...]. If it appears soonish, it is should put more affordable Used D810s on the market. The D4 and D5 cost too much and are too heavy for my budgets.
Yes I agree with Richard, DX and FX are complementary and we have superb Nikons in both classes
kind regards
woody