Hi @JakeM, welcome to our Community!
If I understand this right, you wish to know more about storing your Dropbox folder using an SSD drive, right? Provided you mean something different, please clarify.
Keep in mind that it's highly advised that you not store the Dropbox folder on an external drive.
If you boot your device, and the SSD fails to connect or isn't read properly, that could result in files being deleted from your account. It's rare, but it can happen under certain circumstances.
I hope this helps!