sounds fine to me! women always need more space then men. my vanity area is 66" long and I'm thinking of putting in something like a 24" cab with a 15" drawer stack next to it and a 24" (or so) lower counter top to the left of the cabinet. something like that is great for putting on make up or doing your nails. neither of which I do much of any more!

Don't know if there is a "standard" size. We had all our bathroom mirrors custom framed as we needed sizes that fit our own individual needs. In the powder room that meant a mirror that would work with a 7' ceiling and for dh who's 6'3". Not easy! The mirror is 26" x 38". The vanity is 52" with sconces. In the kids bathroom we needed mirrors that would also work for much shorter children AND tall parents or guests. Here the vanity is 84" with 2 sinks and lighting above the mirrors. The mirrors are 24" x 36". The ensuite bathroom has a vanity that is slightly shorter but also with two sinks and lighting above the mirrors which are the same size as in the kids bathroom. All mirrors have frames that are 2 1/2" or 3" wide. I like the look of mirrors with wider frames but that wouldn't have worked with the function we needed, i.e. work for short and tall people.

I think it would look better the way you planned. We are just finishing a gut-reno of a 6'x12' master bath with 2 vanities on perpendicular walls: one 30" and one 36". I only just noticed after they were installed that the sinks are different sizes (its noticeable when you stand at one, then at the other, but not when you are just in the room looking around). It is functional for us as DH likes a large sink and I don't. That said, just do what is functional for you. The aesthetics of it really aren't going to be noticeable from 10' away especially b/c one vanity is longer (so the eye won't notice the different sink sizes as easily I'd think?).

This would depend on your space and the size of the vanity. Do you have any pictures of the space or measurements that you can provide?