I don't understand those questions. Google Drive is webdav to the best of my knowledge. Anyway, it works out of the with Gnome/Ubuntu. When you connect a Google account, a drive icon appears. Doesn't get more "native".
I get the problem that most vendors don't have an app for Linux, so some functionality is lacking compared to what you may be used to. And cross-platform anything can be a problem, i.e if you really need Linux Desktop + Android + Windows + Apple stuff. (I do and learned to use web-based applications for work.)
What do you really expect from a "Personal Cloud Storage"? not a clearly defined term.
Seafile (needs a paid server as the backend) works nice for syncing files. Google Drives works as network drive. There are tons of backup solutions that work with tons of storage backends (aka professional cloud storage).