So, having been left to my own devices to pursue this one so far, the best I can find is that storport.sys sometimes led to some users having similar latency issues.
The advices in question tend to be:
'just re-install windows 10 bro' - Never works, I have done this procedure with probably twenty PCs, and it's the equivalent of taking a jackhammer to an uneven floor; furthermore, I want to know precisely why/what is going on, and this doesn't help with that;
'switch from RAID to AHCI' - I don't know enough about the fundamental differences these make to know, and I'm constantly scared of screwing up anything that affects hard drives. I've got two drives, both SATA, one OS and one storage. I could test this? Would appreciate thoughts. For one, I don't know which I've got running!
'bios/chipset updates' - done. No effect.
'microsoft update' - done. No effect.
'sfc/dism' - done. No effect.
This, the crashing, the constant tearing, it's just so - exhausting. And I've got years of data on this PC, so getting a new PC isn't it either.
I guess my next line of inquiry is replacing the PSU (got the power supply unit) but I want to wait until it crashes/bluescreens so I've got a good point-from-crash to see if it effects time at all if it DOES crash after.