The reason why teutons are more limited by the 999 limit is simple. They produce less significant troop than the other tribes. Not saying they are not good. I'm saying they are less effective in some ways.
For an offensive unit, clubs have the worst Attack point per wheat of the tribes, but their training time is the best, making them the best Attack point per minute of training.
The limit has the effect of slowly chocking out the wheat income until starvation begins. (When you reach a point where 999 raids are providing less wheat than what you Hammer eat).
Of course, every tribes can theorically reach that limit. Guals being second and roman third (because of horse water thing).
Let's say you send parties of 2 infantry unit to raid. Anyway you don't get a full bag... why send more than 2?
If we take only infantry as an example with a lvl 1 barrack:
- You need 5333 hours to train 10k imps
- You need 4000 hours to train 10k Swords
- You need 2000 hours to train 10k clubs
They all eat the same amount of wheat. Early on you can send those clubs much more often to get food early then the 2 other tribes. after only 2000 hours you already have 1 000 raiding party available (the 999 limit is reached here). you basicly capped there.
Gauls cap at 4000 hours. and romans at 5333 hours.
but at 4000 hours, teutons already have 20k clubs. but still only 1 000 raising parties out.
at 5333 hours, teutons have 26,6k of clubs.
Sure they are Killing it. But that Hammer is a pain to feed. This is why teutons are being chocked more in kingdom than in legends. In legend you can basicly send what ever you want... Never saw that limit and I finished first attacker of a server a few years ago. I sent raiding parties every 30 mins all server and at the end every 15 mins. 2 imps or 2 EIs to hundreds of farms (grays or inactives). But that's another story.