Same here with a ASUS Fury. Gpu usage is low and the stutter is very bad.
I have the RX 460 and I am having the same problem, but with more than just quantum break, I am also running crimson 16.9.2
Maybe rolling back to other previous drivers will help you but that did not work for me though.
AMD is probably fixing this issue ( well I hope so), or maybe not, who knows.
5 days and no fix or response.
ps.: I'm not going to buy the Windows Store version.