G21 13-rnd mags will fit and function in the Gen3 G30S and in the G30 (Gen3 and Gen4) and the Gen3 G30SF as mentioned above. The G30S frame is the Gen3 G30SF frame.
The 10-rnd and 9-rnd factory mag for the G30 will fit all of the G30, G30SF, and G30S. They will not fit the G21, of course.
The G36 single-stack mag is unique to that pistol and will not accept any other factory mag alternative, nor can the G36 mag be used in any other Glock 45ACP pistol.
With factory mags and aftermarket equipment there is a wide range of magazine options with the G30/G30SF/G30S to load 9, std. 10, 11, 13, 15, 17, 27, or 30 rounds in a single mag