Martin has pretty much said it all.

Profile rails are much better but are are less tolerant to mounting errors so if you have limited access to tools then you will need to shim and grout to make them level. Otherwise you will lose the advantage of them.

Supported rails can absorb some mounting error but at the cost of rigidity as they have a larger radial clearance. TBR blocks have adjustable clearance so you can maximise their rigidity (data sheets show lower load capacity but I think that is because they are rated with max clearance, need to check that tho.)

For plastic and ali I would go for the 5mm pitch screw to keep the torque advantage. You can always gear up if using belts. Diameter is dependant on length/speed but 16mm should be ok.

There are so many options its probably best to Post some designs to help further. Good luck