Mods are now organized as resources. Use the Mods link above to browse for or submit a mod, tool, or prefab.
The TFP Official Modding Forum Policy establishes the rules and guidelines for mod creators and mod users.
You should use A for instructions. If people want to install it to B, that will work still, but may at some point stop working unless they manually set the User Data Folder to that location, so better to just tell people to use A.
The game folder is for stuff from devs, while the AppData folder is for stuff you install yourself. Microsoft doesn't allow custom content in game directories for whatever reason with GamePass, which is apparently why they did it this way. Keeping them separate also helps to prevent people from deleting the TFP_Harmony mod when they are trying to clear out their mods, which I've seen people do numerous times here. If players aren't touching the game directory, they won't have that problem.
If you're making a mod launcher, just don't do what Vortex did (I think that's the one) and change people's User Data Folder location without permission or notification. It should default to the official location (AppData) and allow users to change it themselves if they want.
Duly noted!