Nope, this is only for you.
The size of Lord parties are in party_get_ideal_size. Here it is:
party_get_ideal_size -1
25 21 1 1224979098644774912 2133 2 1224979098644774913 30 4 0 541 3 1224979098644774912 0 13 1652 3 1224979098644774914 1224979098644774912 0 2204 2 1224979098644774915 1224979098644774912 2133 2 1224979098644774913 10 2170 3 1224979098644774916 1369094286720630785 1224979098644774914 2172 3 1224979098644774917 1224979098644774914 3 2107 2 1224979098644774916 5 2105 2 1224979098644774913 1224979098644774916 2105 2 1224979098644774913 1224979098644774917 520 3 1224979098644774918 1224979098644774914 7 2123 3 1224979098644774919 1224979098644774918 25 2105 2 1224979098644774913 1224979098644774919 4 0 542 3 1224979098644774915 10 1224979098644774914 2105 2 1224979098644774913 100 3 0 3 0 2171 2 1224979098644774920 360287970189639680 2120 3 1224979098644774921 90 1224979098644774920 2107 2 1224979098644774913 1224979098644774921 2108 2 1224979098644774913 90 2133 2 72057594037927936 1224979098644774913
The
lime green 30 is the base party size. The first
red number is the bonus per point of leadership that lords get (default is
5, same as for you), the second is the amount of renown needed per extra troop - also the same as for you. You could tweak the first up or the second down to increase AI lord parties. The
blue number is the bonus that kings get for being kings - 100 default, which is why they run with larger parties.
The limit is then modified by player level. The way this works is it takes the player's level plus 90, divided by 90, then multiplied into the limit. The two
yellow 90's are this section. You could increase the first 90 to basically increase the player's level when used for the equation. If you make it 100, then it would be like having 10 levels above what you actually are. You could also reduce or increase the effect of the player's level by changing both numbers. At 90, they increase the limit by 1.11% per player level. If you upped them both to 200, for example, it would reduce that to 0.5% per player level. If you reduced them both to 10, it would make that a whopping 10% per player level.
Effectively this is just the maximum party size for the lords, they'll still need time to recruit troops and grow to the new number.