Side entry cam cleats for the guy are a good, simple option and ideal for venues with predominantly light winds, as you don’t have the weight of the barber hauler hanging on the sheet all the time. The downside is that it can be a bit hazardous getting old guy out and the new guy in when gybing in breezy conditions.
If you sail in a predominantly windy venue then the other system is probably better, where you have a cam cleat on a raised block on the side deck by the shroud, with a barber hauler just in front of it, so you can pull either guy down or release them remotely from further back in the boat.
As others have said, the sheet shouldn’t usually be cleated on the thwart when the kite is set, for reasons that soon become apparent! However you do need some form of cleat there in order to keep the sheets from hanging over the side when you aren’t using the spinaker.
Some great pics in the Wayfarer Book.