I think when people say increase lag, they are referring to decreasing throttle response (the two are not the same i know, but this is internet ).
As for the understeer, I would definitely go 24mm rear 22mm front. This is great on a daily with maybe a tinny bit oversteer, and yet it's a lot more solid than stock.
I personally think that going 24 rear and leaving the front as stock might create too much oversteer, though I cannot say that definitely as I haven't had the experience with that setup.

Adi