I kinda dislike having game features locked behind perks, these should only add minor things or buffs here and here for features you already can access from the start, just as i dislike that other one where you only get half garrison wages by a perk when it was a base feature everyone had in warband, maybe at max locking the outright buying of fiefs in the perk but you should be able to offer then in trades or a fief for a fief kinda of thing.
Crusader kings 3 made it right their perk tree in my vision, you get all the base features then the perks unlock bonuses here and here and the last perks in each tree unlock a ridiculous feature like outright buying claims in any lands (fiefs), uber prowess in battle etc that is cool because by the time you fully unlock a perk tree you are like half-way or almost at death's door step with that character leaving only a few in-game years to enjoy the benefits of it before switching to you next heir.