fastplace removes the delay of placing blocks
autoplace rapidly places blocks under your feet, depending on which delay you use. different than scaffold because it doesn't just place blocks under your feet, you have to look at the edge of a block (not aim or else you will fall) and hold down right click and once you stop holding it you will stop placing blocks.
with autoplace you can do really anything you want
speedbridge
godbridge
breezily
moonwalk
you can do extensions and clutches
and I think you can telly but It's hard