The gamma in 3.8 was in the middle of the slider and in 3.9 as well, I let it in the middle default settings, since this looks to be the equivalent to it, I checked before if it looks similar.
The normal maps you cannot see much in the screenshots, but they are broken.
Regarding the performance I could not tell, seemed to be a little better, but not much. I could notice significantly less polygoncount, so this should impact performance in some way positively. I will make more detailed tests for that later.