I expect him to switch between forms smoothly, like pre timeskip he would use either G2 or G3, one at a time full body basically, post timeskip he can now use it partially and in sweet spots, same thing should apply to G4 in some sense. It's not even that he mastered G2 to the point where he constantly uses it nonstop, he just uses it in a much more efficient manner, gets all of its pros while minimizing the cons, if he was using it the same way he did pre skip, it would still be quite taxing I'd assume.
So for G4, the transitions should be much cleaner, where he can navigate in and out of forms as he sees fit.