I haven't tried Retroarch on the Switch, but it has a C64 core called Vice, yes. It has a mapped virtual keyboard to one of the gamepad buttons, so it shouldn't be a problem to run any of the games.
As for recommended titles, I'd skip games like The Last Ninja trilogy for instance. It's a good showcase what the C64 is capable of, but the gameplay isn't the best in my opinion.
Ultimate Wizard/Jumpman (although the former requires keyboard during the game, mainly spacebar, to launch a spell. Go with Jumpman)
Heavy Metal Paradroid
Super Pipeline II
International Karate +
Crossroads II: Pandemonium
Mayhem in Monsterland
The library is vast and it really depends on what you're looking for.