The potentiometers should ideally be removed and their old inputs / outputs be bridged.
This would correct the RGB termination resistance to the TV standard
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: