Pretty much anything you try in terms of buffing, sanding, plastic welding, painting will make it cosmetically worse, not better.
Replacing the tank protectors if the scratches are low is cheap and fast.
New tanks would of course solve the problem but are uber-expensive, then you get to scratch them again.
Put a FYYFF sticker on and call it done...
950 Adventure ✧ 950 Super Enduro ✧ 450 XC-W Six Days