I tried downloading
Unity 5.5.0a6 2D Experimental
Example Project 02
83Mb ram was in use, and CPU was running at 35-40%
The demo played smoothly and had a frame rate of 38-42fps at 800x480p, And 30-35fps at 400x240p. It is interesting that the lower resolution had less FPS, but I must conclude that more resources had to be spent to scale down rather then run at 1:1 pixel sizes? The other possibility is the CPU scaled the CPU clock rate due to chipset reaching heat thresholds when testing.
This shows great promise for Unity on ARM Cortex A-53 systems.
I tested at 200x120p and found no benefits at all over running at 400x240p
I also found that using Screen.SetResolution() actually caused a 20-28% decrease in performance over not using it and lettings the UWP app auto target display resolution.
This is in contradiction to my previous tests on unity 5.5.0b4 with that demo we had a increase from 10fps to 20fps.
But over all the new 2D Experimental show a benefit of improved 2D sprite gaming on the system. To the point of 30-40 fps at native resolution. But had a 25% FPS drop when sprites had a rotational transform.
Should be noted the demo tested had far less activity and assets loading in comparison to previous test project.