Besides the pictures and the seller's page, there's no much info about VGA666RGBs. They say it's compatible with Raspbian/RetroPie/etc., so I assume it works similarly to other GPIO analog video add-ons, using the standard vga666 'driver'.

For RGP-Pi, I remember it outputs RGB via Scart, so it might not be the first choice if your monitor has no Scart inputs. Not sure about the driver, though.