I think shielded wire is recommended where there is a 'long' travel eg from the toggle on an LP to the pots, while on something like a fender, non shielded seems to be OK.
I don't think there is a problem with using both types and I thing 20 gauge would be fine (22 for that matter).
StewMacs, GuitarElectronics, Acmeguitarworks all sell wiring kits so you could check what they all put in them.
I haven't decoded the Ibanez wirogram LOL..It takes me lots of time to follow them all particularly when there's p'up splitting.
Regards
Robbo