Threadripper wont suck that many fps out of any card available to reach 144hz, which is impossible to play on 4k but you could on 1440p. But many games do cross 100-130 and thats fine on a 144hz panel. Since you go for a tr and wanna game on 144hz, why dont u buy a 8700k to pair with it It is Waaaaaaay stronger.
To play 4k you are totally gpu bound and could use a way cheaper processor , not that you should but to reach 60fps in a 4k res you could use even a ryzen 1400...
Im stuck in the same situation i wanna go for the 1080ti 144hz on a 1440p res. People ssy if u can buy a 1080ti u can easily buy a 400+ processor thats just bs. So im stuck near 7700k, 1700(oc)which is in my favor due of price cores and decent ipc tho has issues, 8600k witbout the 6 extra threads on a really expensive board, 1600oc to cheap out if needed but prob not. The lower threaded processors are allready maxing out, even the really really powerful 8600k has allready tiny hickups at high settings begging for more threads. However its a beast of a chip for todays market, allthough a bit late...