I've done all of my bath and kitchen counters at 35-36", so I agree with going as high as the base of the window will allow.

I agree with both. 35" in this case.

Most my clients choose 36", but I personally prefer 33", a compromise between the new preference for 36 and the old standard for 30" (which is clearly too low).

As high as possible. I’m only 5’3”, but I love our new taller vanities. Less bending required.

Since you are building the vanity you can do what you want really. The standard now has become 36" tall. In your case it depends if that 36" total height will be either up to the counter or up to a vessel sink in which the 36" is up to the rim of the sink.

Look at this example from Wayfair.

https://www.wayfair.com/home-improvement/pdp/union-rustic-24-single-bathroom-vanity-set-unrs5908.html?sku=unrs5908&piid=25932289

Take a look at the height.

It really depends on how much clearance you want to leave for space.

When building the cabinet, don't forget to take into account the height of the counter surface. We had 36" cabs installed in both bathrooms this past year and once getting used to the new height (after a lifetime of shorties), we really like them.

If your vanity will truly be floating and not in contact with the wall under the window you could even have the vanity at 36". It may not be ideal in terms of design aesthetics, but if functionality for height is the main issue then you have more options by using a floating vanity. Sounds like 35" will be fine though.