Hi, I recieved my Surface 3 this morning and installed LOL immediatly, as it was one of the main things i'm going to do on this little device. Turns out it runs at 30 fps with the native resolution of 1920*1280 and medium settings, while it runs at 45-60 fps in 1920*1280 with minimum settings.
So I think it is going to be very playable, but I did not perform any intensive testing game today.
BTW, I own the 64gb/2gb RAM model of the surface 3
I'll keep you posted, dawg