I think the dedicated motherboard is aw some!!! If they were around when we started (about July 2016) we would have went that route for sure.
The first month was a lot of tinkering with settings and Drivers. But once you find the magic mix (it is different for each rig) the unit will run for months without a hassle.
Our average profit (after electricity) is about $50USD/GPU. But it varies. And you have newer/faster GPUs that should perform better.
Good luck and have fun getting your geek on.