Top 4% as best we know. But I tend to think the difference between the higher ranked players is overstated. A 3.9 player can go head to head with a 4.1 player and not feel completely outclassed.
A 2.3 player will be entirely outperformed by by a 3.2 player. The difference between an entirely average player and at least top 14% is pretty significant.
4.3k is definitely about where 100 SR means a lot. The difference between the players who can consistently hit 4600+ and those who can barely touch t500 is insane. There’s only been a few times I’ve had to face off against someone I know for sure is 4.5k+ (a number of other times I suspect it - a level 45 at 4.2k SR?), and each time I felt like they were able to shut down everything I tried to do. The only games we won against them were ones where we had a player of equal skill, or we made swaps and hardfocused them.
Contrast that to the 4.1k players I frequently face, against whom I still have an impact. They’re still better than me for sure, but they’re not in an entirely different league like people make them out to be.