Hi @Sunshine82, thanks for messaging the Community!
It depends on how the app or service works. If it is linked to Dropbox via the site or API, it might work better than apps that work completely separately.
For instance, when using Time Machine, this could result in duplication or deletion of data, or general syncing issues when files are restored from a backup from their end, because of the way it is processed in the Mac system.
Hope this helps to clarify matters!