playing around with Vincent's vampire appearance, this is pretty much his "true" appearance, or at least the most he can turn into before starting to feel uncomfortable, he can be more "monstruous", like, being more creature than human-looking (as he can pretty much shapeshift his human features to animal-like features, he can even have wings) but he doesn't really like to change his appearence to that extreme

Vincent doesn't like to adopt his true form mostly because in that form he ugly :v...like, he thinks it doesn't look nice and gonna be honest, he's very narcissistic and superficial (most of the time) and doesn't like feeling like he doesn't look appealing, especially because he considers to be attractive/good-looking an important feature to make it easy to manipulate others, but despite of this, he has no problem revealing his true face when the situation requires it as he's stronger with that appearance...or sometimes to scare the hell out of people because y'know, he feeds on negative emotions and fear is one of his favorites :'U

regarding to the outfit, I've always considered Vincent to be very traditionalist when it comes to the clothes he uses and overall his appearance, he's pretty much stuck in 1900's fashion lel, that's why he rarely wears anything more than suits and formal outfits, he's also very fan of old fashioned Vampires as in, the ones that appear in classic movies X'D, his liking for old-fashioned things extends to almost anything from house decoration to his music taste, as he likes classic music and his house is victorian