Mac Pro 5, 1- PCIe Configuration

Here is AMD's Crossfire compatibility chart to help you understand which cards will work together in crossfire and yes x16 and x4 will work fine

That particular SSD card is only able to use 4x PCIe lanes so putting it in a 16x lane slot would make no difference at all In fact all but one

can you win big on slot machines PCIe slots feature the same pin layout and thus are forwards and backward-compatible However, a PCIe card slotted into a PCIe slot will

candy crush slot It's worth mentioning that all PCIe card versions are backward compatible That is to say, any version of the PCIe card and motherboard can work