I don't know about hardware. I use macro to reduce quality on slaves. Quality becomes lower than its possible from the menu. On certain expansions you can reduce 'horizonfarclip' / 'farclip' to zero. Effectively making them blind. Certain variables might give different performance depending on your hardware (e.g. m2Faster). Here is a list of console variables and their descriptions:
https://wowwiki.fandom.com/wiki/Console_variables
/console characterAmbient 1
/console detailDoodadAlpha 1
/console environmentDetail 0
/console extshadowquality 0
/console farclip 0
/console ffx 0
/console groundeffectdensity 16
/console groundEffectDist 0
/console horizonfarclip 0
/console hwPCF 1
/console m2Faster 0
/console farclipoverride 0
/console overridefarclip 0
/console shadowlod 0
/console showfootprintparticles 0
/console showfootprints 0
/console showshadow 0
/console skycloudlod 0
/console smallcull 1
/console timingmethod 1
/console maxFPS 25
/console maxFPSBk 4
/console maxFPSLoading 4
/console violenceLevel 0
/console WeatherDensity 0
/console ffxspecial 0
/console ffxGlow 0
/console ffxDeath 0
/console gxVSync 0
/console spelleffectlevel 0
/console terrainMipLevel 1
/console waterDetail 0
EDIT: I just discovered that you could also disable camera adjustment which allows you to keep looking at the floor (and reduces strain on GPU). Not very good for targeted abilities though. The with slaves do:
Zoom in:
/script SetView(1);SetView(1);
Then manually look down on each character. As long as they are looking down on floor fully zoomed in they should not consume too many GPU resources. When zoomed out i got 15 fps in city, when zoomed in i got 60 fps.
You could also take it one step further and save and load the views the first time you find the correct zoom and pitch.
Save angle camera angle for character:
/script SaveView(3);
Set camera to the saved angle:
/script SetView(3);SetView(3);
You might need to do "/reload ui" on first logon of the saved views won't load according to:
https://wowwiki.fandom.com/wiki/API_SaveView