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, 12900K, BIOS 4001, MEI 2433.6.3.0, ME Firmware 16.1.32.2473, 7000X Case, RM1000x PSU, ASUS TUF OC 3090TI, 2 x 16GB Corsair RAM @ 5200MHz, Windows 11 Pro 23H2, Corsair H150i Elite AIO, 4x Corsair RGB fans, 3x M.2 NVME drives, 2x SATA SSDs, 2x SATA HDs.