If Couriers want a good guy with a good heart, good brains, and good aim, then Arcade might just be a good fit. Joining the Legion locks him out of companionship.
However, energy weapons are still the best. Imho the Minigun is the best closed range non-energy and AM-Rifle best for mid and long range.
And it just so happens that seemingly good-boy Arcade has a not-so-clean past with them. This Machine works at above medium range, has a good sized clip and allows for more shots than what you would get from a Sniper up close, and especially in any vault type area. Within the Fallout universe, the Enclave - the last remnants of the US Federal Government - has been a recurring antagonist throughout almost every game.