IMO the 3rd version is probably the best, but you really should turn the ends of the screw down.
I have the dual bearing design on my machine and its not ideal, unless your machine is dead square, level and perfectly aligned your going to have a slight misalignment in the screw from one end to the other. The thrust bearing design allows for some play but keeps the back and forth motion rigid which is important.
You will only need one thrust bearing on the screw side of the block, not the motor side.
You will want another thrust and regular bearing combo on the other end of the screw.