I worked with a recent version of UE5_Main, and WPO and masking actually seem to be very performant. I’ve gotten over a million masked instances running in real-time at a high frame rate, and WPO seems to be coming along nicely. I understand how the original version of Nanite works, but how they support WPO and masking to me just reads as absolute sorcery.
Also, just for a bit of Trivia, Nanite actually does use imposters-but so far in the distance that it’d be impossible to notice. 