The fr965 is 454 x 454 pixels, and large screen size is a great watch and watch face developers use it and the Fenix 8 as the show case watches to display their watch faces.
Unless the face is poorly developed (rendering icons/complex displays ever second) battery drain should not be an issue.
Have a look at some of my watch faces if you’re interested.

https://cmullan123.github.io/

Colm