Can I delete photos from my phone after uploading them without deleting them from Dropbox too?

Here's the process I've used that seems to work: move (not delete) the files from the Camera Uploads folder (on Win or Mac) to another folder. I move the files to folders named by date, such as 2016\01_January, 2016\02_February, 2016\03_March, and so on). 

Once moved (not copied or deleted) from the Camera Uploads folder, Dropbox does not upload again (because they've already been synced from your mobile device (phone/tablet) to Camera Uploads. Once I've moved the files to another folder, I can delete the images from my mobile device. 

Now here's the caveat! I have a windows PC with lots of storage. I also use a MacBook Pro with less storage plus an iPhone and iPad. I take photos on all devices (except the PC) and don't want to clutter up my phone, tablet or MacBook with excess photos. BUT Dropbox must be able to sync somewhere and for me that somewhere is my desktop PC. So when I move files to my PC, they are still synced with Dropbox and I can delete off the other devices. I do selective sync with the other devices (most important on the MacBook because otherwise it wants to sync all Dropbox files on its limited storage).

The same approach could be done using an external drive on your Macbook. Dropbox would upload files automatically to your Camera Uploads folder, you'd then move them to the external drive and free up space on the (probably) more limited MacBook storage. Make sense?