Also worth noting – the SNES Mini/jr. does not natively support RGB. All other SNES’s do. If you have a Mini/jr., it will need an RGB mod.
Strongly suggest to stick with HDMI out for the 360. There’s a video floating around on youtube comparing X360 SCART SD line multiplied, to X360 HDMI HD. HDMI HD looks much better.
If needed, to simplify things, get a 3-in/1-out HDMI splitter, or something that would suit your needs to support your HDMI native devices and OSSC (3-in/2-out, 4-in/2-out, etc etc).
Just my $.02. 🙂