yes… but I assume you own a 4K montitor , because you mentioned you switched back from 4K to WQHD. So, you can try out 4K now easy by your self 
The performance is improved a bit, but magic wonders will not happen here. User can not expect a doubling of fps in 4K. Most important are stable fps for eg. 30 ( or in my case 37.5 fps ) , and that I get often, but not allways.
Thus, 4K is in same kind worth to use, as pre SU10.
About quality diff 4K vs WQHD was already lot mentioned. WQHD is still a good compromise if you need more fps. But 4K is 4K and the quality is better.