For MC you only need 1 ASI and Ethel's hair for 20 main stats.
For companions, 2 ASIs will take you to 20 / 16 / 16 in 3 stats if you min max and dump 3 stats to 8.
As for feats which offer +1 stat, they are very limiting and only the Str ones offer something else good (mainly Athlete and Tavern Brawler).
TWF or Ranged feats dont offer +1 dex, so its hard to bother with them except for the extra feats rogues or warriors get, but rogues are better off with 2x handbows, fighters with a 2H weapon.
Theres a feat which gives saves proficiency to the +1 stat you pick? Yet the stat you would want to use it for on any class, they already have proficiency in those saves.
The bigger problem IMO is you get too few feat slots to really benefit much from choices other than ASI, especially on companions. For casters you really do want 20 main stat and warcaster, so for caster companions there goes all 3 feats as nothing else is as good.
The popular multiclassed sorc / wizard / tempest cleric, you only get 2 feat slots, and to really make it shine you need elemental adept: lightning, so you get 18 caster stat and that if its done on a companion.
