I haven't experienced any compatibility issues yet, but please report any you may find. I did find one weird bug though:
When you use the relax key, you will automatically sheathe your weapons, before sitting down. This works fine, unless you're within 256 units (approx. twice the length of a Nord) of a shrine to one of the aedra AND you have a shortsword drawn from Heavy Armory. It simply doesn't play the animation in that oddly specific case. If this ever happens to you, just tap the relax hotkey, and then hold it down to relax... the animation should then play. But for now, i really suggest sheathing your shortsword before sitting down.
I must say, that this puzzles me.
I'm a big fan of Frostfall and RND, so I'll be working on integrating my mod into their systems, so that they may combine and influence each other. (ie. Getting thirsty when exercising or getting cold more quickly, when heart rate is low)
Right now the mods don't conflict at all, and sitting on a bedroll from frostfall will actually be relaxing