Yeah you have two good choices that would offer big upgrade.
I had a 1080ti with a 5Ghz 8086k (basically a binned 8700k) as well as a 2700X rig. With 1440p high refresh, the 8086k had a big lead. I upgraded the 2700X to a 3700X, and while it was an improvement, there was still a noticable gap in more demanding titles in the pursuit of 90+ with mixed detail settings. When I upgraded to a 2080ti, it only got more noticeable. I had initially planned on phasing the 8086k out and fully replacing it with the 3700X, but instead decided to just run two PCs : one for general use, and another purely for high refresh gaming. I upgraded the 8086k/Aorus Gaming 5/3733 ram combo to a 9900KS/ASrock Phantom 9/4000 ram combo, slammed it under a DH15 Carbon, and run it at 5.1 to 5.2 depending on the situation. This combo often gets me 30+ fps/20% over the 3700X.
So you have two good choices. Going to a 3600/3700 range CPU will get you a boost you will be able to feel. It will also let you probably (assuming at least a 2xx Mobo) go to Zen 4000 series when those come out. A 3700X is just a better, more efficient option for general purpose PC work than Intel 9000 series. Added bonus you can probably use your existing Mobo.
Other option is a Z390+9700K build. This will give you the absolute best high refresh gaming experience, but is an upgrade dead end. I don't think this is necessarily a terrible option though. It seems like the trend is HEAVILY headed towards just adding more cores per segment, with outright clock increases grinding to a basic halt. And unless Zen 4000 solves the cache/memory latency factors that chiplet architecture necessarily creates, it holds it back in edge cases like high refresh gaming. That's not a knock against it, for the vast majority of regular PC use, the benefits of lots of cores and cache overcomes the latency hit, and it makes high core counts possible in a way that monolithic designs can't easily approach even in the most extreme cases.
Either way you're looking at big boosts over Zen1, which was honestly pretty bad as a match to a 100+hz gaming setup. Just with different pro/con in each direction. It's a hard decision lol, which I why I just decided to do both