The old design of seatpost clamp had a horizontal bolt that could be tightened on each side. The only advantage of these was that you ccould remove the whole clamp from the post, flip it around and mount the saddle forward of the post for a time-trialling/triathalon style (this is really old-school british TT racing from the 1950s).
Otherwise, they are heavy and coarse to tune.
Std ones have a single vertical bolt.
A modern alternative is a 2-bolt design: The 2 bolts are forward and aft of the post and allow fine-tuning of the tilt. This is my favourite type.
Saddle rails are all pretty standard so you can switch clamp style. Do get the correct diameter otherwise you can damage the frame. It should move in the frame like a piston.
You can spend a lot of lightweight posts but unless the rest of the bike is lightweight , you wont notice any difference.