The F-7PG is an entirely different variant as compared to the 'P/M/S/A' versions.
The structural differences include new wings which are strengthened and reinforced to carry more payload. The addition of raked wing tips give the aircraft capability to sustain sharper turns making it more versatile. Plus a 3 piece canopy (F-7P) was replaced by a single piece one which is much simpler and safer to operate.
Other differences include the replacing of Italian FIAR Grifo-Mk-II radar (F-7P) with the Italian FIAR Grifo-MG radar system which has increased detection range and can track multiple targets aswell. Further more, indigenous electronics from PAC Kamra and AWC Wah Cantt make the the F-7PG an entirely different aircraft as compared to its other variants in service with PAF. Those electronics include ACMI system and so on.