If you are using a other card you can go with riser 1 doesnt matter so much.
Can you explain me why is the riser 2 better for rx470 and rx480 ? I think the difference is that version 2 is using power supply 12V only (you can use independent 12V power supply) and other versions need 12V and 5V. The disadvantage is that linear regulator heating more than other versions, due to higher voltage drop.
The PCI plug On R2 , the plug is the issue on most of the other ones they burn out to fast etc .. so far sense i switched to the boards with PCI plugs , Ive had no burn outs it seems more stable and use a 16 gw wire.
to be honest, i don't think it matters..Ive had more trouble with the molex Plug type, no issue yet with the PCI type, doesn't say i won't, just not yet .