Im stuck on what size mirror will fit best here and would love any input. I want to install a lighted mirror and am looking to go with one single mirror. Likely, this one here.

https://www.ibmirror.com/lighted-mirror/dimmable-lighted-mirror-harmony-85-x-40/80

They have in-stock options up to 100" wide and 45" high but there is also an option for custom widths up to 110".

I feel confident that 45" high is a good option (I have that marked with painters tape in photo) but I don't know if there is some ideal formula for choosing the width so that it is proportionate/aesthetically pleasing.

My vanity is 125" wide and the height from top of backsplash to ceiling is 61".

Any and all input is much appreciated. Thank you!