Looks like I need to create an arranged Documentation for it (I have literally missed pointing the relation between the main things).
The script goes together with Marin's Pokeride and hence the first v1 has provided the 7 mounts available with Marin's pokeride. You might be aware that this whole thing was started by UlithiumDragon for their game on v16, which he gave to my friend (PokeMVDeveloper) and he gave to me(yeppp its a chain), he had made many custom pokerides. You can find the showcase of his mounts here-
https://www.pokecommunity.com/threads/400872 So, basically, the additional mounts provide functionality for these 17 mounts. If you want to use all mounts not just default 7, first follow installation from main folder, then open additional mounts folder(no need to copy v1 script). From this additional mounts folder, copy graphics and pbs, follow installation and copy the script. This installation is kinda complicated, so there I have provided Pokeride_Main edited version if you don't want to follow installation. And that's the difference.
If adding 7 default pokeride mounts, ignore additional folder, else follow the above process. (I think I shall provide a copy of PE with pokeride installed with a pokeride map)
Following Pokemon Ex? Looks like you are using v18 essentials. This Ride Pager script is for v17 and might work smoothly with Mej71's Following Pokemon(I haven't but PokeMVDeveloper has tested it). Since there is no official v18 release of Pokeride by Marin, the ride pager is also not released for v18 either.