The CPU in that system draws up to 45W, and the GPU between 60 and 120 W of power -- the battery cannot supply that power by itself.  The system just cannot run at anywhere near full speed on battery power alone.  You need to decide which is more important -- CPU speed or the GPU (you can run the CPU faster by running the game on the integrated GPU rather than the nVidia), but if you want the system to run at anything resembling decent levels for gaming, you need to plug it in.  
Operating SystemWindows 11 Home 64-bitCPUIntel Core i7-11800-H @ 2.30GHz 57 °CTiger Lake 10nm TechnologyRAM16.0GBMotherboardDell Inc. 0284MK (U3E1)Graphics2047MB NVIDIA GeForce RTX 3060 Laptop GPU (Dell) 56 °C     Playing rainbow, after unplugging is night and day difference. I changed the minimum cpu thing from 5 to 100% did all the battery settings. did the battery thermal settings in the my dell app. This is legit crazy. Iv tried throttle stop and nun works. I have yet to oc or under volt. those are the last options.
Dell G15 5511 11800-H Throttle / loss of fps / unplayable. After unplugging 
from battery