Both over the tire and the tie down should be ratchet. Either or is as good as the other.
With the over the tire style you should use 4,.. one over each wheel.
With the tie down style you SHOULD use 2 in the rear and 1 up front. Odds are if your in an accident you'll be the one to hit something and the 2 in the rear should stop the car from breaking loose off the trailer.
You SHOULD,.. also use a separate safety chain up front,.. or any other type of securement just as a backup in case your single front ratchet fails.
Some trailers with a winch,.. they use the winch as a single tie down up front and then 2 safety chains on the rear and use the tension of the winch against the rear safety chains to hold the car in place. And again,.. a dedicated safety chain should be used up front in case the winch comes lose.
As for how to hook to the car. The around the tire straps pose the least stress on the car,.. but certain types of the over the tire straps have a tendency to come loose as the car rocks back and forth on the trailer. If you choose this style,.. you want the ones that have an adjustable loop and wrap around the tire and have a ratchet on only 1 side of the strap. 2 in the front for each tire toward the front of the trailer,.. then 2 in the rear for each tire toward the rear of the trailer. The style that locks to the trailer behind the tire and then goes over/around the tire and then clamps to the trailer again are the type that come loose.
I personally just use regular ratchet straps to D-rings on the bed of my trailer. They make T-hooks that lock in the frame,.. these are good if you have a strong piece of frame for them to lock into,. Mustangs have good T-hook slots. The other style like what I use is to just to loop the strap around a piece of the suspension,.. A-arm, axle or anything strong,.. clamp it to itself and then ratchet the car tight. I've never had my cars come lose. The regular ratchets can also be used to hold down things like lumber, plywood, kitchen appliances, jet skies, pallets of cinder blocks or anything else you might want to load on your trailer.
Hurst