Any riser is fine tbh. As long as the adapters you're using are the ones with yellow and black wires (those are thicker compared to the rgb ones), you are good to go.
The best riser would be the one that matches with the perifs of your PSU.
As for the molex connector, if you aren't experiencing any trouble with your rig without it plugged, then don't worry about it.
if you gonna go that route you for sure want 14 to 16 Weight wires they usually come with 16 weight but be care full, Ive seen some sold as 16 wire with the black and yellow cable. and it came with 18, not good ...
an by what your saying that's the 16 wire .