Regarding the CPU thermal soaking diagnosis, try to do a Cinebench run. If you score sub-average, could be a liquid metal/PTM issue. If your score is good in a repeatable way, thermals aren’t an issue.
You can check here for many, many results on both 7840HS and 7940HS in Cinebench.
Also, check out Framework Control Center, an user-made service+GUI lightweight tool to manage and monitor TDP, temps and noise. With that you can see how much watts your laptop agrees to pull with/from the charger and can set fans to run 100% (very noisy but should help diagnose thermal problems).
I also recommend you DDUing the drivers away completely and reinstalling the driver pack.
You can also reinstall the BIOS running the .exe again… It helped some users in old releases (can’t find the posts right now, it was around the 3.06 release IIRC).
I used to run Helldivers 2, AlE IV and VR games like Pavlov VR or VTOL VR with the 7700S with both 180W and 240W chargers without stuttering or issues. Don’t surrender, when you diagnose the issue and games are smooth you’ll thank yourself 