I honestly prefer just using right alt as a AltGr. Even have a custom Windows layout to re-create (parts of) the "US International (with dead keys)" layout from Linux/X/GNOME/wherever it comes from.

Instead of having to type <Compose ' o> for a ó, I just type <AltGr+o> (or alternatively, <AltGr+' o>, and similarly <AltGr+` o> for a ò)