You wouldn't be emulating the game yourself, the emulator (retroarch) would be.
All this addon does is give you a list of systems to choose, once chosen it then lists all roms available for that system. You would then select the rom which is then automatically downloaded to a temporary folder which then automatically launches retroarch and loads the game. I believe the roms are downloaded from archive.org it can also grab all metadata. Once you exit the game and back to the rom select screen, the rom is deleted from a temp folder. You do have options to store the game which helps for the bigger games (psx etc)
One of the best addons I've ever seen, has so many platforms I wouldn't normally think to play, and all metadata and artwork is already setup