IMO Troglobite is the very best path.
Upside: Quick, Regeneration, disease immune, str +4, full night vision, slimy (immune to DOT component of acid), light eater, and a few other perks.
Post Thresh: Eat corpses, happiness buff underground, str -2 dex +2 (not worth post thresh IMO, but it isn’t terrible either)
Downside: Albino, sun sensitivity.
No matter what category you go for, you can take Troglobite afterwards to cure ponderous, fast metabolism, and deterioration without risking cancelling any natural attacks.