Some do run jets but you'll get better performance and handling with a prop. Especially low speed.
As far as getting on plane most of these type boats are flat bottom or near flat bottom skiffs. Sitting still, they are essentially on plane. In other words, you don't have to get the hull up out of the water or on the pad. They pretty much sit at the same attitude they run at.
These boats are designed and BUILT specifically for this whereas an aluminum boat as example has a tunnel as an after thought. An option.
You ever seen a propped boat go over a sand bar? These setups can. You make a run at the dry sand bar, as you draw close you drop the power all the way off, wait for the wake to over take the hull and float across what was once a dry sandbar adding power as necessary.
It's all in the timing.
It's a pretty extreme form of fishing especially in south Florida and West coast Florida where you have miles and miles of flats
I used to converse with a guy who builds his own boats in Florida right regular. Plywood, glass, and epoxy. Really nice flats boats.
He left the dock one morning and 3 miles out hit a mangrove stump running 45mph. Jerked the stump out of the bottom of the sea bed. He drove back to the ramp. That stump drove up through the bottom of the boat and stopped before it came through the floor. I saw the pictures. The stump was still hanging out of the bottom of the boat.
He had poured the hull full of foam so he didn't take on any water. Foam displaces water.
Pulled the boat home and repaired it.
Cost wise, a true flats boat will set you back quite a bit especially the radically powered ones.
You could build a 20x8 flats boat for around 10 grand including new engine. It's just not going to have speed but will have the skinny performance. Start looking at boats like the Hells Bay and you are looking at 30-50,000 for a 15-16 foot narrow beam boat with a 70 mph capability in inches of water. It's a different world down there.
When it gets to the point you are incorporating carbon fiber fabrics and laying Kevlar on the inside of your hull to keep objects from coming through the boat and potentially impaling occupants, you are getting serious with it and slinging money around.
Heck, 6oz hybrid Kevlar 50 " wide which aint much protection is about 40 bucks a running yard. They are using something in the neighborhood of 12 -17 ounce.