Difference between "Captain" / "Army Commander" / "Party Leader" regarding Perk bonuses

[David Goggins]

So, what is it referring to in each of them? Like how do I know to who these perks affect?

I assume Captain refers to the leader of the formation you're in (so if MC is leader of cavalry then the captain bonuses only apply to cavalry?)

Army Commander bonuses should apply to every single troop no? Since you're the commander of the whole army, even if you're only the "captain" of a single formation

Party Leader affects only companions I assume? or why is there a distinction between party leader and army commander?

[Ruffio]

Captain - Applies only to the formation they lead.
Party Leader - Applies to your party. (straight forward that).
Army Commander - When you lead an actual army that have several clan parties in it.

[p30pl3h4t3m3]

party leader = leads the party (and assume not assigned party roles like scout, medic, quartermaster and so on)
army leader/commander = leads the army, a pack of partys, defines pre battle troop groups and assign captians 2 troops
captian (or however its called) = leads assigned troop group in battle

perk description reveals what bonus works in a specific role

[Action Man]

Army Commander is pretty straight forward. For formation bonuses, you can hover your cursor over one of your captains (and the pre-battle setup) and press Alt. It will give you a detailed breakdown of the specific bonuses they apply to a formation/unit. I think it also tells you the perk that gives the bonus.