I have mix always at 100% and a slight tilt because of my hearing loss.
In my first attempt in room treatment I didn't take professional help and had much too much of absorbers and not enough diffusers. Often the main problem are too many thin absorbers which will take away your highs so that you get a dull sound.
I built myself a simple vocal cabin then and so always had too few highs in the vocals but a lot of boom and mud.
Now I use the whole room with a good mix of absorbers and diffusers.