If the clamping force on the 770’s is too high, you should be able to gently bend the metal part of the headband outward, either with your hands or by leaving it stretched on a shoebox overnight.
The headband padding has snaps, and if you open those, you’ll see that the piece underneath is just a solid piece of spring steel, so it’s fairly resilient to some gentle bending. Lots of folks out there bend their headphones to reduce clamp.
Beyerdynamic used to make a “Premium” version of the 770, just like they do with the 880 and 990, that had a gentler clamping force…but I think its sales numbers were too low and they cancelled it.
You could attach 880 pads to your 770…but the isolation will be reduced, and the sound signature will change a little bit. Also, since their foam is less dense, the odds of them running into your ears will go up as the cushioning will squish more easily.
The Beyerdynamic Treble(tm) is an infamous feature of all their products that seems to inspire a lot of love-it-or-hate it responses online. I happen to love it, and I totally understand why some folks don’t. It can be quite sibilant depending on whether the material you’re listening to has lots of energy where the treble peaks, particularly in the DT990. The 770 and 880 are a touch less harsh, and I find them exciting and fun to listen to.
I’ve always thought of the 770 as an M50X, but a bit more aggressive.