Are emulators allowed? Is there a recommended one if yes?

The rules don’t say it isn’t so I assume they are allowed.

Figured it would be worth checking, I know some games ban them or only allow certain ones.

Well, most games ban MOBILE emulators, due to their inaccuracy.

Any emulator will probably be fine as the game is non-competitive at the moment. If you are worried about future-proofing your runs I'd definitely run on Bizhawk with mGBA core or just using mGBA (either one with a BIOS file is optimal) as they are the most commonly accepted in GBA speed communities. If you have any questions or need help setting it up or anything feel free to ask here or message me