There used to be a button to do this, but I haven’t seen it for years.
Never been a thing in Classic.
Turn off Shadows, Sunshafts, and Liquid details.
Turn Spell Density to Dynamic.
Turn off VSync.
Everything else can be on or Ultra unless you got a toater.
Always recommend you to cap your in game FPS to 2 below your hertz on your monitor. You get 20-50 ms less input lag.
No it totally used to be. I think they removed it during TBC.
https://www.youtube.com/watch?v=ec7IGxwtYRk
Even 5 years ago it wasn’t a thing
you are right. I distinctly remember a recommended settings button 
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