In questions of Speed (bounties or regular rifts) personally I prefer swk wol Monk. That's the screen clearing bell. It got buffed a bit since sweeping wind can now stack up to 13 stacks from 10 pre patch. Due to in'geom negating the cd of dashing strike completely u fly through zones. Just kill a pack every 10 secs.
Nearly every class has a more or less fast Build. It's up to your preference.
May be check YouTube for
D3 S19 Barb Speed
D3 S19 wizard Speed
And so on. U should find something there for sure.