AMD Ryzen 7 3700X / GeForce GTX 1070. I started noticing slowdowns while moving through balls at around 1200, and by 1400 it was a permanent slideshow. The speed at which I can add balls and increase the limit appears to depend on the frame rate, so I did not have the patience to check much higher numbers. About 15 minutes spent total, nausea at a 1 or 2.
I expected to be able to float up while floating, but it seems like I was still constrained to planar movement.