Jones having faster hands just means he does indeed hit harder as he's generating more force via acceleration, so he's the harder puncher
Jones didn't meet much worthwhile opp at 160 (Hopkins and Tate), so looking solely at that weight doesn't give a great sample. But how well he carried his power up to 168 and 175 must reasonably reflect on his power at 160. He blasted guys like Malinga, Sosa, Griffin, Hill among others in an awe inspiring manner. GGG had nothing like that even at 160. Speed was a good part of Roy's KOs, to be fair.
It's worth noting Tate went the distance with Julian Jackson in a very tough fight , and only last 2 rounds with Jones. Which is a feather in the cap for Jones regarding his power.
There’s more to punching power than speed. Speed helps a lot but Ali was not a great power puncher and Forman was. Speed can help you get kos because you hit opponents with punches they don’t know are coming. Something that happened for Jones a lot more than GGG.