Welcome to the ROG forum.
I don't own a laptop but for a laptop, you have to admit that is some beefy specs.
How is room temperature?
Have you considered a laptop cooler?
The stuttering and low FPS is likely due to either the 12900H cpu or 3070 ti thermal throttling or both.
To get a better idea of temperatures, could you do this for me?
Install HWinfo and click on the Sensors tab, this will bring up all information about your laptop, including clock speeds, voltages, and temperatures.
Under Installer in Bright Green click Free Download, then Local U.S.
Once you have it installed and opened on the Sensors tab, play a game until it starts throttling. Exit the game and make HWinfo full screen, take a screenshot and post it for us. At the top, make sure we can see the maximum values of all readings.
This will give us a better idea of what's going on.
Click the picture to make it bigger
Thank you, this helps tremendously.
What this shows is the i9-12900H is thermal throttling due to high temperature, the 3070 Ti temperature looks good with a maximum of 76c.
When the cpu temperature hits 90c, that's when thermal throttling starts.
Is it still thermal throttling with the fans at 100%?
Show us a screenshot with the fans at 100% after playing a game.
Before doing so, reset HWinfo by clicking the clock on the bottom right.