My games runs fine so far, beside the creature thing.
I witnessed Nemesis and switched from FNIS used these steps:
1. Open Fnis > deinstall Creature behaviour
2. Deleted Fnis
3. Installed Nemesis
4. Re-installed every single animation Mod (+Nasty Critter/Framework)
5. Run Nemesis to create behaviour
6. Sorted stuff and started game
What happens is that the creatures stand still. Not static T-Pose, they just idle while my character is doing the ani