Usually play with view distance and spell effects maximized, everything else down rather low.
And then limit main screen FPS to 60 and slaves to 20 FPS.

I've lowered most of the settings, for the main screen.
But now dynamically have maximum view distance on the active toon.
And much lower view distance on the slaves (minimal).

Overall, my graphics are a bit higher on the main, then before.
And I can switch from any toon, to any other and retain the higher settings.
Also the switch speed is instant, as before.

Still tinkering around, but am currently using (as my Higher Settings):
/console farclip 1250
/console groundEffectDensity 64
/console groundEffectDistance 260
/console environmentDetail 40
/console particleDensity 100
/console shadowMode 0
/console waterDetail 0
/console reflectionMode 0
/console sunShafts 0
/console basemip 1
/console terrainMipLevel 1
/console projectedTextures 0
/console weatherDensity 0
/console componentTextureLevel 2
/console textureFilteringMode 1
/console Sound_EnableAllSound 1