Does it make a man feel masculine to have a big bank account?
Not in and of itself.
If men believe that a big bank account attracts women, then one believing they have a larger bank account than another man may lead one to feel more masculine than the other (and vice versa). Of course, it depends on the culture. This may very well be the case in some cultures and not others.
Whether or not you share in my specific understanding, it is well documented that masculinity is cultural.
Even if no one knows his salary or net worth?
It’s all about perception, so what is actually true doesn’t matter. Certainly if one portrays themselves as having a high salary/net worth - e.g. driving expensive cars, wearing fancy watches, living in big houses – that may lead men to believe it. No doubt that is why men do exactly those things (at least in my culture).
If no one sees your pink underwear in public would it challenge someone’s masculinity to wear it?
Anything is possible. Again, perception, not reality. No one actually seeing your underwear doesn’t mean one isn’t thinking about the possibility of it being revealed. What if it slips out? What if you get into an accident and healthcare workers need to remove your pants to save you?
Having shinier peacock feathers doesn’t necessarily mean you are the more virile bird, but if that’s what you’ve got you are going to play it up to make other males think you are the one who will win the female’s attention.