I was testing retroarch as a multiplayer option with a friend and wanted to know if it is a valid emulator?

The core used in retroarch is Final burn neo

Retroarch can be used since it is compatible core for other gaming systems like Mame, SNES9x, FBA-FBNeo, and other ones and also used for Retroachievements. The only exception in Retroarch is the usage for smartphone/android which most leaderboards won't allow it.