1. Since there are only 3 cable options for the N64 on “retrogamingcables” is the Sync On Luma a better/more compatible choice? I will ask the Modder about those specific details.
The manual for Tim Worthington’s N64RGB board states:
The board supports both (PAL) Super Nintendo RGB SCART and Gamecube RGB SCART cables.
With that in mind, RGC’s regular GameCube SCART cable is probably what you’re looking for. The OSSC can get sync from CVBS or luma, so there shouldn’t be any need for a cable with a sync stripper.