iMac 4k - best used at 100% or 200%?

[strawbale]

Not knowing nor understanding the technical ins & outs of the HiDPI scaling in OS X, I seem to get from various threads (here and elsewhere - sorry no links at hand) that Mac's with 'only' integrated graphics, like the 2015 MBP 13" with an external 4k (3840x2160) monitor, may be laggy when not set at 100% (which would make text too small for most monitor sizes) or 200% (1920x1080 equivalent), as any other setting needs more processing power. Is this correct and, if so, does that apply to HiDPI settings on a 4k iMac as well, given the lack of a dGPU?

 

[Jeff Flowerday]

Just use the default for display. It will perform the best.

 

[strawbale]

default being 200%?

PS: I'm all the time assuming keeping the screen in native resolution, ofcourse, but te question is which hiDPI setting(s) perform best with an integrated GPU (like the iMac)