There are 2 Strive games, Strive for Power and Strive: Conquest, which use "Strive" and "Strive for Power 2" respectively. There is no game that uses "Strive 2", though it is possible to rename the "Strive" folder or change the path in project.godot to that. But for a vanilla install it's simpler to just stick with "Strive", which should generate when you start the game. Ignore folders by any other name, at least until you have a better idea of what you are doing
The current version of Aric's mod is 1.1. The current version of Strive is 1.0d, but the next version is pre-released by the Bugfix mod which alters v1.0d. Neither of the mods is compatible with 0.5.25, you will need v1.0d. The Bugfix mod is required to be pre-installed before Aric's mod can be applied, as there were some bugs in the mod system of vanilla 1.0d.