I had a very similar situation with my previous Z390 Gigabyte build. I spent months trying to sort out the problem, every combination of software, drivers, BIOS settings, updates etc etc. I even compiled a very comprehensive spreadsheet of every change I made. I would get 2-3 bluescreen crashes daily for no apparent reason at times. I even replaced the PSU to eliminate bad voltages but that didn't help either. I can't comment on WHEA errors as I wasn't looking for them at the time. But yes, like you I could stress test the system and it would usually pass. My keyboard and mouse would also become unresponsive occasionally, so I changed those too and purchased a new external USB hub.
Anyway, turned out that I had a faulty USB cable connected to an external device (which happened to be a software controlled radio board|). So, I suggest that you plug in just the minimum number of devices and try different cables where you can. No idea if that will help, but worth a try I think. Also, have you checked EVERY cable and internal connection to the PSU and motherboard?
Last idea for now, have you reinstalled Windows and/or reformatted that SSD drive?
Z690 Hero, BIOS 2204, ME Firmware 16.1.25.2124, Corsair 7000X Case, RM1000x PSU, i9 12900K, ASUS TUF OC 3090TI, 2 x 16GB Corsair RAM @ 5200MHz, Windows 11 Pro 22H2, Corsair H150i Elite LCD AIO, 4x Corsair RGB fans, 3x M.2 NVME drives, 2x SATA SSDs, 2x SATA HDs, 2x 4K monitors.
"If you're lazy like me and do nothing else in life, be nice to yourself and back up your data today" 🙂