[2020] Difference between buildings/props?

No, props are decorative and don't really do anything. At most they can have cars parked (like parking lots) or people sitting on them (like benches).

If people can live in something, it is a building for sure.

This guide also covers a lot of the words you will meet on the workshop and explain the differences.

https://steamcommunity.com/sharedfiles/filedetails/?id=1411897315