^^Welcome to the Forum.

I just checked the Ford.com website and it looks like the ST-Line is only available here with the 2.3L Ecoboost engine. IT does not show it as being available as a PHEV in North America. The largest engine, the 3.0L Ecoboost (400 HP) is available in the ST and King Ranch.
As for the wheels, I'm guessing they are the same and the same guidelines would apply in that the new wheel/tire maximum diameter difference should not exceed 3% compared to OEM. The ST-Line and ST both have the 255/55R20 size according to the Ford website.
Peter