I posted this elsewhere but I'll leave it here too. Besides using the included installable 3DS .CIA file (which will have visual limitations):
FYI -- the game runs perfectly, and looks fantastic, on: https://github.com/profi200/open_agb_firm (recently updated too!)
On mGBA, even with hardware boosts, I can't get the game to run quite as seamless (especially during cutscenes). I'm assuming this is either due to the limitations of the 3DS hardware when it comes to emulation performance or mGBA needs to be updated to be further optimized..? As it is, unfortunately GBA emulation doesn't get too much of a regular focus in terms of maintenance in the 3DS modding scene, I suppose.
You do have to trade off some of the inherent benefits of using the emulator though (save-states, optional screen widening, etc.). If there's any suggestions for better methods of running GBG on a N3DS, def share!