saiyan78 I didn’t set a standard controller for ps2. I just use my ps3 controller for all sony consoles. I didn’t recognize any problems if there’s another controller connected. Maybe check (in advanced system or advanced game settings) what emulator is used. I use the standalone PSX2, but there’s also a retroarch PSX2 emulator which may be used as standard emulator if you didn’t change it manually. The retroarch emulator handles some things in another way than the standalone emulator.
I don’t have any experience on how to handle the controllers if more than one controller is used at the same time for Sony consoles.