A texture of size 600x600 will look roughly the same, no matter what resolution the player will play in.
If the game runs in a higher resolution, then it automatically scales-up the entire UI. If it runs in a small resolution, the UI is downscaled.
The only difference comes from different aspect ratios, in which case there is some extra space available on screen.
https://wiki.esoui.com/AddOn_Quick_Q...pact_the_UI.3F
If you have a texture control of size 1680 x 1050, then it will always cover the entire vertical space or the entire horizontal space of the game window.