No game sync?

Eco uses a local dedicated server for singleplayer, there is no cloud storage. To move your save game to a different computer you need to move the /Steam/steamapps/common/Eco/Eco_Data/Server/ folder, respectively at least the Configs and Storage folders within, if you don't use any mods.

The avatars are also saved locally (although in AppData and the registry), but once you join a server with a specific avatar it will stay for the whole lifetime of that game and can only be changed at a dresser in-game, new avatars or changes made with the main menu do not apply to servers / games already joined.