Vinnie not saying anything is meaningless, actions speak louder than words...
VInnie being more succesfull then Quinn is nice for him but best take out the competion first, next step is taking out and replacing Buddy.... Selling stuff for other people is really not the most profitable way.... Get people to do the running for you.
Vinnie went to the Dik mansion to get something from the safe and to get something from MC room.... The girls just happened to be there.... Vinnie may have heard from Nick about the MC but he meets MC first time in his room....
Why would Vinnie want to teach somebody he doesn't even know?
That is the thing. I think Vinny has been observing the house. As I said before he holds some grudge. He left the college. He certainly have a grudge against the diks, but I would be more specific and say he has a grudge about Rusty and Tommy who are also the frat's founders. I wont create theories on what it is.
People created a theory about Nick. I haven't seen Nick doing anything wrong yet. So this is an old theory that people keep going on with only because his room was the only room that wasn't trashed.
I am pretty sure he is around oberserving the college, but specially Quinn and the dicks. Reason why Riona feels someone is watching her. And since MC have been around all of them, and have already fought for them and he saw that MC has some skills he came to show his fangs, but wasn't even enough of a man to deal with MC without a gun.
He wanted to mess up the party again and wanted to mess up with the diks life, he couldn't do that since the safe was "safe" this time.
So I think he just took it to the room of the guy who took his room and the guy who has created changes in the mansion, and has been actually running things in the mansion and as tommy said: "He is very successful on everything he does". Reason why Vinny decided to brag about being one of the founders.
Ofc Vinny is pissed he isn't getting his way around anymore and he knows MC is the reason behind it.
On my point of view, he is feeling threatened reason why he decided to scare MC off, but he just made MC aware of him.
These observations above is only taking in consideration things that have happened in the game so far, without putting any ideas or creating theories in things that no one has seen.
The same goes to Quinn's business. People are reading so much into it. Quinn is just a drug dealer and sometimes a sex worker, we don't know how much she does, because since she is the one in charge of running the money for "tuition", she doesn't exactly have to have sex for money unless she wants to (I think she chose to deal drugs specifically to not have to do sex for money, but that doesn't exclude her since she have done a restaurant meal for MC and could have done the same for others as well). We already know she loves to be in charge of things.