Does it matter which DisplayPort slot I use if there's multiple DP ports

In general, the port priority is as follows: DVI; HDMI; Display Port ; DisplayPort ; DisplayPort GTX 900 Series

Traffic Filtering > Ports and GigaStreams > Port Statistics and Counters > Display Port Display only those ports that match the specified box and slot IDs

display port slot Slot Count Allocation to VC Payload monitor or TV for driving the display component from a display controller

displayport slot port on your PC supports DisplayPort technology DisplayPort adapter cable can be used to provide DisplayPort display capability