A texture atlas is a double edged sword. You can have extra data that will reduce texture updates, but if you have too much in the atlas you will drain available vram.
It would only be a 100% usefull if none of it goes to waste (all “slots” are used at all times)
You also need to leave some room for post processing and other effects that use vram.
And im not sure if it would work with mipmaps well