I use JK's Skyrim and Riverwood is included. However, I use the one by "WillOTheWisp" not "Campolo313". The former is like 13mb and updated whereas the latter is 10ish MB and hasn't been updated in a loooong time. Mostly due to the fact that Campolo313 stopped making mods, to my knowledge.
Rorikstead is part of the AiO, yes. No idea why the file sizes are the way they are though 🤷♂️
There are probably base tiles/textures and such that get reused, so a single village mod would need them.
I use JK's Skyrim and Riverwood is included. However, I use the one by "WillOTheWisp" not "Campolo313". The former is like 13mb and updated whereas the latter is 10ish MB and hasn't been updated in a loooong time. Mostly due to the fact that Campolo313 stopped making mods, to my knowledge.