In general both on my own benchmarks and from what I've read/seen youtube videos, it's about a 5% performance loss multithreaded with full core saturation and 0-1% performance haircut on single threaded -- since on single threaded you are generating lower enough heat not to go near the high end.

For me this was going from 105W to 65W on my 7700X and my results were similar.

Not sure how it would look or work with Intel though.