I used my Herpstat for my CHE before winter hit (I had to switch to using both heatpad and CHE bc my tub's a lot longer and my che wasn't really cutting it by itself....), and as long as the ambients are right on the hot side my hotspot was dead on. I tend to like my hot side a bit cooler though, 86-88 degrees with the hotspot varying 88-92.

It depends entirely upon what you put beneath the CHE. Like if your hotspot is a hide, or some slate rocks, then you just make sure the temps are ideal and if not adjust the temps on the thermostat accordingly. Just like the dimmer, only you're not messing with it constantly because the thermostat does it by itself for the most part. You'll just have to adjust the set temp until you reach what you want.

You've already proven that this setup works for you. You'll just have to find that perfect set temperature for the thermostat that mimics you messing with the dimmer constantly.