Which units would you replace in the Sylvan castle?

No, what are you talking about! The archers in the Elven faction are clearly male! It's only in the fourth game that they were female. In my opinion, the best Elven archers are the unupgraded ones from the third game. In the second game, they were some kind of Elven Georgians.

Added 3 minutes later
I have nothing against Georgians (well, except that they pursue an overly aggressive policy), but Elves should be fair-skinned and have light-colored eyes! By the way, according to Tolkien, they should not be blonde, but dark-haired: in his works, only a few Elves had light hair.