performance on quad core i7s

Are the 6+ core chips going to be necessary for good performance in the long run? I see a lot of the videos running on Intel's HEDT chips and they are running much better than I'm able to get with my 7700K (unless something's configured wrong on my end). I realize the PS3 has more than four CPU components to emulate, but I'm not sure how many threads rpcs3 is using.

With Ryzen 8-cores and upcoming Intel mainstream chips reportedly moving up to 6 cores (finally) it probably won't be an issue in the long term it's just something I'm curious about.

One game thread is one real thread with no distinction. For some ultra heavy games like Persona 5 you will see a benefit from more cores. For other simpler games there is no gain (except for some general performance improvement thanks to more cache maybe?). For example Atelier runs almost as fast (or slow) on an i3 as on an i7.

Anyway, RPCS3 can become a lot faster in the future, but some edge cases like games based on the FrostBite engine (and some more) do use every SPU for rendering so they may "never" be fast enough on a 4 core CPU, but who knows, these games don't work yet anyway so we can only speculate.

But today and for almost every game a i7-7700k is just fine. If it isn't fast enough it's likely no other CPU is either and you would have to wait for RPCS3 improvements.