Not much to say. Can solo entire armies with Louen alone, even on VH, which is not balanced for SFO. And generic Bretonnian lords are not much worse. Generic Bretonnian lords in SFO can 1 vs 1 most legendary lords with ease.
In SFO Bretonnia has an insane economy, one of the best in the game. Their late game is probably the easiest: grail units and lords are just way overtuned in SFO, and due to how Bretonnia works (no extra upkeep, upkeep reducing minor buildings, +2 armor for everyone for each armory...) you can spam and spam armies of unkillable cavalry and flying units. They can force confederations with extra bonuses per confederation. Their campaign objective is probably the easiest in all WH 2.

At least a nerf on the lords and heroes would be appreciated. It's not normal I'm getting so many kills with paladins with almost no hp loose. And it's not normal to see Louen regen 2 times his life in a battle.