The heavy suddent FPS drops sometimes crash nvidia driver too and close the editor. Very strange the issue appear also when not playing. Could be looking into some forest or house structure and suddently FPS drops to near 1 and stay around it often some 10sec before returning to smooth again (e.g ~50fps). Heard there is some win10 related leak. Cant wait to see it fixed if it helps. Else looking good. 
i7 5820K, 32Gt DDR2400, GTX780, SSD Samsung 950pro, Win10 64bit.