I had the same problem with an I7 + RTX4070 (HP Omen) laptop. The fix was a motherboard swap that HP did under warranty. Problem was the CPU faulting immediately into thermal throttling once the game booted up.
It took a good couple weeks to get to the root cause using every CPU tool I could find and some back and forth with their support.
Quick test you can do to see if the same is happening on your laptop:
Configure at least two desktop screens in your Windows environment - Use the Ctrl+Win+left/right cursor to switch.
In one screen run the task manager (shift+ctrl+esc), go to performance screen and show all CPU cores - note the reported CPU frequency - Should be in the ~1.5GHz range at idle. Many cores will be idle.
Switch to the second screen and launch BG3 - let it boot up to main screen with the music and 3D cinematics.
Switch back to the screen with the task manager - If your CPU is any less than aggregate ~ 3GHz (usually higher) and closer to the idle 1 - 1.5 GHz - same defect I experienced.
Give it a shot and see if this is the case on your system.
If you want to dig deep, the utility "throttle stop" helped pinpoint the error after a rather steep learning curve - nifty tool but needs lots of learning on the users part.
