I just ran the fishies at 3000x1726 on my new Hi13 in Edge, and I got about 24fps for 1000 fish. I also ran it on my original 2013 Surface Pro, at 3840x1814 (by zooming smaller), capped at 780 MHz, and it got the same results. At full power, it was getting twice those results.
But really, this isn't bad for an Atom chip. I was playing Minecraft at 640x400 on my Stream 7, so I'm still expecting to use a lower-than-native resolution.