Using Dropbox with Mojave
I upgraded from Sierra to Mojave on a MacBook Pro (2016) and iMac (late 2017), for the wrong reason, it turns out, but mostly I'm happy with the outcome. Ever since I started running Sierra on those two machines, I'd been plagued by what I first thought were spontaneous unmonitored (that is, when I wasn't actively using the machine) reboots. Turns out, the machines weren't rebooting, just logging out of my user space, and only because there's a System Preferences>Privacy and Security setting to do just that that began with Sierra. Even though it took a massive disruption in my daily work to expunge that behavior (a correspondent informed me of this setting), I now have an up-to-date OS.
I did my updates by "Clean Install" from backup clone boot drives created in "SuperDuper!"; i.e., I erased my boot internal SSD (MacBook Pro and Fusion Drive (iMac) and ran the Mojave installer while booted from the respective bootable clone drives, then used the installer to "pour" my user accounts, apps, and other files back into the new installations. When I did so, the installer asked me whether I wanted to use iCloud Drive to manage several types of information; e.g., PDFs from Preview, videos from QuickTime player, and everything from Dropbox.app. This last puzzles me.
The way I use Dropbox is as a private but multiply-located file cabinet. While iCloud Drive accomplishes many of the same goals, they differ in one respect (and more), in that iCloud Drive will use my behavior to manage my internal boot volumes' data storage as the volumes fill close to capacity, by keeping just a pointer to some of less frequently used actual files on my boot volume, keeping the "reference" completed file in the cloud for retrieval when needed.
It seems to me that using iCloud Drive to manage what Dropbox has been managing is redundant; i.e., if everything I now store in my Dropbox folder is automatically copied into iCloud as well, there will be TWO local copies of those files, filling my boot volume twice as fast. Am I not understanding this correctly?
Thanks so much for any responses.
MacBook Pro 15", macOS 10.12