A couple of lambdas have been changed to references for a tiny performance increase and clearer code
Variables, classes and arguments are now marked as final/immutable where possible
We now get the instance of Minecraft once and reuse that reference where possible to save a tiny bit more memory rather than getting and using new references of the instance every time
ShouldYellAt32BitUsers is now true by default as 64bit Java is beneficial even for Vanilla users due to increased performance and increased default and max render distances.
From Paint_Ninja on CurseForge :)