There is no question that the vanity is very traditional, and certainly not simple in its lines. However, I am not one who says everything in the house has to be the same. One nice thing about a powder room is that it can be a 'fun room', a little jewel that offers another feel in the home. So, I think indeed it could work, and be very fun. As for the wall stencil, while it feels more contemporary because of the black and white, the design feels traditional, and could very easily work in the space. In fact, the design of the individual unit in the stencil kind of picks up on the center design of the cabinet door. I would think about adding light fixtures (ceiling if you have one, and over the vanity) that have a modern take on traditional lighting. Something like this, that has the crystals but done in a modern way. crystal rainfall overhead

I love the godmorgan sink for their clever plumbing moving the ptrap to the back so that you can have drawers. I got one but my plumber threw up all over it for the cheap quality of the plastic in the plumbing. He did agree about the design and is building ours with the ptrap in the back so that we can do drawers using better quality stock parts. Mirrors.. I would suggest picking this first as this will drive much tile you need. Have you looked at IKEA mirrors. They are a good price point. Also home goods etc.. Faucet.. Online prices are much better.. Do you like the look of the faucet in the picture? I went with a simple version from a good quality brand for my regular bathrooms with a single lever. For powder room, I also wanted it to be fun and did wall mounted in antique copper.

What about the bar pulls on the 4 larger drawers and a knob on the two smaller ones? It would cut your expenses, plus solve the dilemma of different size bars. I just looked for my inspiration pics on knobs/pulls for my bath remodel, but I must have deleted. With apologies for yet again posting pics of my vanity....this is what I did. Not exactly the same set up as yours, but you can at least see what I mean. The small drawers are just false fronts on really long drawers, just to visually break up that too long expanse.

Bold blue in powder room sounds terrific! I can't find my SW fan deck, so frustrating! But here's what I did and it worked. I have an area rug in my bedroom that has lots of colors, but there's a particular muted green/blue color in it that I like. So I got my SW fan deck out and tried to find a close match. It ended up being SW Silverpointe. I looks like gray in the fan deck but it has a green undertone (if you look at the darker colors on the same card, you can see what the undertone is). There was one other color that was a candidate that had more of a blue undertone, but I chose the Silverpointe. You can only see the undertone if you paint a large area. So for you, if you have a favorite color in a piece of art, pottery, clothing, etc, find a close match of that color in the fan deck, and then move up the card to the lighter colors. Using that method has helped me to choose light colors with the right undertones throughout my home. I used that same method in my great room. There is a horse painting in there that has a nice blue/gray tone on the horses neck, and I matched my wall color to that, just slightly lighter. Good luck!