A 1x riser can be used in a 16x slot.    
https://i.imgur.com/iNNzmnt.jpg

Those ribbon extenders can be powered, but are old fashion 
https://i.imgur.com/e5asEwb.jpg

use these
https://i.ebayimg.com/images/g/3vQAAOSwWxNY0~Mv/s-l300.jpg