Syncing Cloud Drives for the Home User

Many of the videos use the word backup. As a new to NAS user I am curious how I can remove Google Drive and OneDrive from Mac and use the NAS to synch to the cloud versions. I think the Packages may do two way synch but are they secure? What happens to your passwords?

The video would be directed at the home user and show the options and set up for the most common cloud services. It would focus on not just backup by synching, including timing etc.

The idea is to free up hard drive space. What do you lose with the NAS method?