Creatures Caves

The Steam version's bug fixes are redone from scratch rather than being based on community patches for legal reasons. In one case they actually introduce a bug (specifically, the fix for the DS elevators meant to fit grendels into them sometimes permanently freezes creatures), and I would recommend replacing that with a community patch. Otherwise, speaking personally I haven't had much of an issue.

It's worth noting that installing replacements in the Steam version can be a bit funky. If you ever need to use the "Verify integrity of game files" option, it'll undo your changes if they're named the same as the originals. Since most patches were made before the Steam version existed, they don't take that into account and will get overwritten. It might help to keep a list of everything you replaced just in case (or just never verify integrity).

As for the genomes...if you're finding the vanilla genomes are working well enough for you, there's no need to swap to a different set of genomes.

If you do want to use a new set of genomes, CFE and TWB/TCB are the two most commonly used in the community nowadays. The latter are the most advanced genomes currently available, but require some extra patches to work their best with the game. The former are basically upgraded vanilla genomes and are more or less compatible with the vanilla game. And there's other options other than just those two. It all depends on what you want and the amount of setup you're willing to put in.