Question for disk base emulators

for emulators based on disk load systems: ps1, ps2, dreamcast, ect
can i just play the iso off the emulator, or do I have to get a mount program first? I have not tried disk based emulators before.

It depends on the emulator, most can do either. Load the image directly, mount it to a virtual drive, or burn it to a disc and read it in a real drive.