Well... let's see. Time to eat some humble pie I think (or maybe not.. no idea), since after almost a week of trouble-free BG3, my PC froze up on me again a couple of nights ago.
This time it happened when I was alt-tabbed out of the game, browsing the web.
The only errors I can find in the Reliability Report now are for Microsoft Teams Updater. I went and removed Microsoft Teams from my autostart and it's not running now, but the error for the updater keeps popping up every day.
Going to have to look into this one again.

But at least the launcher isn't crashing anything any longer. Those Teams Updater errors are almost always around the times I've booted up the PC and nowhere near the one freeze/lockup I've encountered. I've started with uninstalling MS Teams altogether, since I don't need or use that thing anyway.
If anyone can "read" this, here's the error report (German OS, but the entries should explain themselves to those with more knowledge than myself, I suppose):
Pfad der fehlerhaften Anwendung: C:\Program Files\WindowsApps\MicrosoftTeams_23231.411.2342.9597_x64__8wekyb3d8bbwe\msteamsupdate.exe
Problemsignatur
Problemereignisame: MoBEX
Vollst�ndiger Paketname: MicrosoftTeams_23231.411.2342.9597_x64__8wekyb3d8bbwe
Anwendungsname: praid:msteamsupdate
Anwendungsversion: 23231.411.2342.9597
Anwendungszeitstempel: 64ed3548
Fehlermodulname: ucrtbase.dll
Fehlermodulversion: 10.0.22621.608
Fehlermodulzeitstempel: f5fc15a3
Ausnahmeoffset: 000000000007f61e
Ausnahmecode: c0000409
Ausnahmedaten: 0000000000000007
Betriebsystemversion: 10.0.22621.2.0.0.256.48
Gebietsschema-ID: 1031
Zusatzinformation 1: 3475
Zusatzinformation 2: 34751ba47c3d88e3a0db2dc402540d6a
Zusatzinformation 3: b3b5
Zusatzinformation 4: b3b523383d789603cbbf23bf44834359
Weitere Informationen �ber das Problem
Bucket-ID: cf4e5287b056f74ccb0ce2c70a1e301d (1949182083240701981)
I suppose the updater and MS Teams itself are two different apps and disabling Teams alone will not disable the updater. Haven't found an obvious way yet to disable that thing, though. I already did another File Systems Check, which came up "clean". As it should have since I ran it only a few hours after the rather large Win 11-update from a couple of days ago.
*shrug*
I'm starting to wonder if there's something more fundamentally wrong with my PC. Then again... none of these CTDs or hard-crashes ever happened before I installed and started playing BG3, so ... yeah. The errors probably were there all along even before that, but since the PC or other games never crashed on me like that, I never bothered looking into the logs. Ignorance is bliss, I suppose..

EDIT: Just went over to the "Win-Geeks" board again and folks recommended I should use gpedit.msc to prohibit Windows Update from messing with any of my drivers. Reason being that Windows Update *might* install an older driver over a more recent one that was installed manually. Other than that, I didn't get any more insights into this particular crash, but then again there isn't really a logfile or even a detailed entry for it to work from AFAIK. I guess when the PC just hard-crashes/freezes without even a Blue Screen Of Death, there's not much for the OS to log, other than an abnormal shutdown of Windows.
Again: What I do know is that this PC has been crash-/trouble-free, running other demanding games on a daily basis since March/April 2022 (when I built it) and that all the trouble started pretty much *exactly* on the day I installed BG3 and then became really bad with the Aug 25th patch.
S.