How would you describe the appearance of a guy named Vincent/Vinny and what Ethnicity do you think for a guy named that?

Vincent sounds like a British vicar/priest with back air and black rimmed grasses, Vinny sound like a British gang/motorbike thug with black greasy hair and acne

I know two Vincents, and I have a character named Vincent. So I pretty much thought of all three within nanoseconds of each other.

The first Vincent is tall, blonde, blue eyed and incredibly good looking. He's also very obviously gay and takes great pride in being a stereotype because it annoys his very conservative Christian family.

The second Vincent is short, Korean and very intense. He stares at your face little too hard when you're talking to him. He wears his nails a little too long. Not sure if that's cultural or if it's just him.

whatever appearance you want, Vincent is a moderately common name

Names have absolutely nothing to do with appearance, ethnicity, character - anything.

It depends on many factors