Hi,
Unfortunately the PSU you linked to is pretty terrible for arcade stuff, it's weak and can give video interference. Not recommended at all for PCB games, but it just might be enough for Pandora's Box.
For OSSC you can use the NESRGB Scart cable or a VGA cable with the right adapter for HAS (listed in the first post of this sales thread).
Unfortunately the PSU you linked to is pretty terrible for arcade stuff, it's weak and can give video interference. Not recommended at all for PCB games, but it just might be enough for Pandora's Box.
For OSSC you can use the NESRGB Scart cable or a VGA cable with the right adapter for HAS (listed in the first post of this sales thread).

fixed. 
