If the app is designed for it you can use a hybrid approach, where a given "document" is stored in 1 file for each client, and the client merges the changes acr

If the app is designed for it you can use a hybrid approach, where a given "document" is stored in 1 file for each client, and the client merges the changes across all files. That way there's never a change conflict that something like Dropbox needs to handle and it can all be offloaded to the app.