Ok, I had figured it was a VK-105 since it topped at @ 415mph.
A Yak-3 is still a 400mph class fighter, with a very good climb rate, and like I said, is much more representative of the VVS fighter force than a Yak-9U.
As far as how good it would be? well, like a Yak-9, but faster, and with a much better gun package for air combat. Also it has a one piece canopy at the front, and I like its forward view better than the Yak-9s, and you don't have to try to aim that silly howitzer of the Yak-9T.
They modelled a Yak-3 in Warbirds, and it was quite a nifty ride. They also have them in IL-2.
I would expect it to be more like a Spit XVI-ish in performance, I am generalising only, but since you asked...
Imho it was the supreme dogfighter of the VVS in WW2, better than a LA-7, LA-5FN, Yak-9 or a P-39N, and most of the other lend lease a/c they received.