Actually, the 1440p benchmarks weren't all that jaw-dropping at all.
Scratches head smiley required.
On my end the difference was minor; stuttering was reduced a fair amount for me. But unlike you I'm also still playing on a 60fps framerate limiter in Nvidia control panel.
On paper there was a 400MHz difference, but I went from a Zen 2 Core 0 that couldn't maintain 4250MHz effective, to a Zen 3 Core 0 that does 4850MHz effective all day long. So more like a 600MHz+ difference. Moreover, Windows scheduler tried to keep loads on the best cores (Cores 5+7), but often times the load inevitably came back to Core 0, which is even more a problem because Core 0 and Core 7 are literally on opposite ends of the chip in different CCX. On the 5900X the load never goes outside of Core 0 and Core 1, Core 1 is actually slightly better and hits 4.9GHz effective sometimes.
Also apparently I can't RMA my 3700X without "proof" that I've at least attempted AMD's "very useful" troubleshooting suggestions that I've already done and said I did; I'm not risking my 5900X's pins just to get some 3700X screenshots for AMD's bonehead support dept, and there's no GPU output if swap it with my 4650G.