allow Dropbox to run regardless if a user is logged in

You have two separate issues. One is VPN related. The other DB. We run Dropbox as a service on our server. Often after setting it up as a service I have to go into the Admin account, log into the client and make sure all the settings are correct. The "Service" version will adopt those settings. It also tends to auto update itself successfully to new versions. However Windows updates sometimes bump a log out on the DB client and you have to go back in. BEWARE! When this happens and the client has to be logged back in and files need to be indexed, the cloud versions supercede the local ones even if they are newer. This a horrible Dropbox bug. Granted you will have the new ones but marked as conflicted.

Local workstations can edit files on the server and they sync to the cloud by the server automatically.

Remote users are of two flavors. Company "roaming" computers have the DB client running in their user account and receive file updates via DB cloud service via full or selective sync. Non company computers from either employees, contract employees or consultants use their own DB account and we share folders from the company account. We denote those folders on our end as "xxx- Shared" so we can keep track as they are all over our tree.

We do not use VPN to get remote machines back into the server shares. That is rather antiquated, slow and unreliable. You might as well just use remote desktop in that case to minimize data loss.

You cannot reliably sync multiuser databases, such as accounting, this way. You can also sync two servers at remote locations. Since DB prefetches, sync's complete the moment the file is closed. There is no file locking across the connection though. But, for unreliable connections it's a great solution.