How much pressure/torque on "stabilization" jacks?

my TT had scissor jacks at all 4 corners
my 2001 cardinal 5th does not us scissor jack in back, bit another type of jack system that goes all the way across. it does screw down.

is this older system as good as the scissor system.
also thinking of putting a scissor jack system just in front of wheel, I see many different brands. my distance is 24". is it better to put blocks in so the jack does not go all the way down?
thanks