I picked up a Asus Prime H270+CSM on sale at Microcenter.
It has 2x PCIe x16 slots
4x PCIe x1
2x M.2

so should be able to use max 8 cards which is the max I want to use in a rig.
Will be hooking up 3 Vega 64s. That's all I have for now.

Thanks guys