For a dual port card, you will want an 8 lane PCIe 3.0 slot connected to the CPU. Almost any desktop CPU will have enough lanes since you won’t be using a graphics card. You can get by with a 4 lane slot, but you won’t be able to max out both ports bidirectionally at the same time.
Be absolutely sure that you get the source and destination drives correct. If you get them backwards, it will nuke your data. There is no confirmations, dd will start as soon as you press enter.