VPX doesn't really need more CPU as much as it needs more GPU. I'm running it just fine on a Pentium 3220 with a R7-250E graphics card, very budget build, bearing in mind I don't have the graphics all set high. After playing enough vpx, I've removed vp9 from both my cabs, physics wise and visually vpx is so much better it's hard to go back, so I quit doing so, there is enough out now on VPX to keep me happy and more all the time. But yeah, if you can barely run vp9 then vpx isn't going to do well.
Setdmd still a nice way to set the default location, gets it close on the 2 screens, then you can just use the mouse to size and position from there, no need to edit the registry to set the dmd locations.