If you feel the need to manage your cores on your own, here's a strategy that has worked fine for me on i7-6600k and later models in the series.

Client 1 = 1,2,3,4
Client 2 = 1,2,3,4
Client 3 = 5,6,7,8
Client 4 = 5,6,7,8
Client 5 = 3,4,5,6
dxNothing = 1,2,7,8

I'm sure I'm probably doing something wrong there but I've had no issues running 1080p @ Ultra on the main with the detail macros set up properly to limit the background windows. And I usually watch Netflix/YouTube and have an unholy amount of tabs open while this is going on. I just don't have issues with crashes, stalls, etc.

With your 6/12 CPU, I'd probably run clients 2 and 5 on cores 9,10,11,12 and dxNothing on 1,2,3,4 with client 1. That's pure theorycraft, though, as I've never run anything other than bog-standard i7's.