Sorry that the wiki isn't up to date yet, but basically the mod has the following things at the moment:

Rails:

Crossover Rail - super simple, I know, but something that really should be in the vanilla game.

Prismarine - These work underwater and emit a low level of light. Standard variants + Crossover included.

Lumium - These emit a very high level of light. Standard variants + Crossover included.

Minecarts:

Underwater Cart - Holds a large amount of air which replenishes when it surfaces. Continually fills the air meter of the rider, if it has supply. Can be enchanted with Respiration.

Various TNT Carts. :)

More stuff is coming! This is 1.15.2 only for the moment, but will be ported up ASAP.