Depends. You can take as long as you like planning the turn. You plan everything your four units do first then the whole lot is executed at once. Executing could take a up to a minute or two - haven't timed it. You can replay over and over with slow-mo and fastforward too. I'm planning a lot more controls so you can see the action in as many ways as possible - like a single units viewpoint.
The video link above shows a very quick turn. Using one unit and one command. That's not unusual, you don't have to move all 4 units if you don't want to.
The video link above shows a very quick turn. Using one unit and one command. That's not unusual, you don't have to move all 4 units if you don't want to.