These knights are only available to faction Spain and Portugal and no one else.
Going to crusades helps in getting the knightly order guild for that faction quite early as it gives +25 points(you need 100).
But taking the faction leader doesn't gives any extra points the game considers it as a general and nothing else. Though it makes the papacy more happy if a Leader or a heir joins and goes to the crusades.
btw the a old cheap trick to get a guild pronto is just before u storm the crusade target make all the generals in your home country to join crusade and after that conquer the city in the same turn. U get a guild, chivalry and morale bonuses and it makes the pope go super happy.
For any guild type you get +25 points for joining a crusade and +10 points for recruit knights from it. Apart from that only the hopitallers are Teutons get a bonus of +10 points if they share a border with a region that has islam or pagan religion respectively(have to be more than 50% and is one of the reason i don't capture stettin early in my HRE campaign).
We also get a +10 points if a catholic nation declares war on a islamic factions(Hospitaller guild only).
A chivalrous general having chivalry 5+ also gives a bonus of +5 points every turn in it's settlement.
That all u need to know about getting a Knightly order guild.
