Low pressure aeroponic (aka LPA) NFT hybrid, with spray nozzles inside the rails would probably be the best growth..
As far as which way to drill the holes.. Well, the wider & flatter the channel, the better suited for just a standard NFT system IMO. If just trickling water in from one end that is. The roots will have more area to turn into a matt, being fully saturated in the film, unlike with round pipes.
I think if going with spray bars inside, then going the taller vertical route with the clone collar\plugs on the end like you have it propped up might work better.
Not sure what you'll be growing in those (I could see small clones rooting, etc), but you might need to space out the plant sites to allow for bigger root systems if actually trying to flower cannabis, if even possible. As in, one plant per tube. Those look to be 2x4". Check out stinkbuds 4x4" NFT aero rail systems to get a better idea of what to expect, with rails that are 2 times thicker.
I prefer the bigger vinyl 5x5" over the 4x4 fence post sleeves myself, with extra room.
The rails you have there appear to be perfect for smaller plants and herbs though. Lettuce..
