I don’t recall ever have had to resort to grub shell.
I usually use a rescue stick
[root tip] [recovery] Basic Manjaro Linux Rescue and Recovery
The laptop I have as test system - with Nvidia - is with my daughter while she is waiting for her own to come back from Lenovo - but it would be of little use as it uses Nvidia 5070 and envycontrol is working as expected.
When you report this - I do vaguely recall something about envycontrol not working with 16xx series - my apologies for, unintentionally, sending you down a blind alley.