I've played around with different core and video settings combinations and here's what I'm using right now with satisfactory results:

Core 1/2,7/8 - Slot 1, graphics Ultra
Core 3/4 - Slot 2/4, low-quality renderer
Core 5/6 - Slot 3/5, low-quality renderer

I have run my setup using low settings for slots 2-5 but found switching to low-quality renderer gives much the same appearance as low settings and gives significantly more fps on my slot 1 session.

Also, my experience is that the gpu difference between low setting and ultra is minimal while the cpu usage goes up tremendously. That's why I have 4 cores assigned to slot 1.