The potentiometers should ideally be removed and their old inputs / outputs be bridged.
This would correct the RGB termination resistance to the TV standard 75
Ohm.
With the potentiometers in the path, that termination is closer to 65
Ohm, which results in a slightly darker picture.
Removing these can be tricky though, since you can't reach the pins with a clipper. Desoldering is recommended.
This is not a necessary modification though. The brightness can be corrected with the software or on the display.
Here is how the connections can be bridged: