There are so many options at 20, I don't know why Broncos would give up a pick to move up.
This is my current first round big board:
Guys that very likely won't be there but are instapicks if they fall:
Guys still on board near 15 or so that would be value at 20:
OJ Howard
Corey Davis
Zach Cunningham
Ryan Ramczyk
Christian McCaffrey
John Ross
Cam Robinson
Teez Tabor
I have no problem with Broncos picking up a CB or edge rusher in the 1st, even though they would be depth in year 1. Take the rare athlete, they are ... rare.
There will be at least one of these guys available at 20, and any of them would be a solid pick.