Best answer by Baldrick
Webroot Backup & Sync is not, I believe, an imaging tool, per se, like Macrium Reflect, etc. but a backup tool. And the concept of differential & incremental only relates to the former.
As far as I am aware Backup & Sync will backup, i.e., take a copy of, whatever is registered to Backup & Sync. There may be some logic/intelligence like checking to see if current file is the same as the current back up, i.e., in the event of no change no backup is made. But I have seen no evidence of that with my use of Backup & Sync.
What I would say is that if yo are looking for a solution that provides differential & incremental images (and therefore by default Full image capabilities) then you should look elsewhere for that. There are plenty of capable solution both free & paid out there.
Hope that helps?