If you utilize Android, I recommend OpenVPN for Android, which allows you to specify which apps you want to push through the VPN per VPN profile/connection.
- For example, you can configure it to only apply to the ownCloud app, with all other app traffic being routed normally.
No. Much like OpenWrt with LEDE, there were massive disagreements within the devs and maintainers of ownCloud back around 2015ish, of which led to a mass exodus of the aforementioned from ownCloud, with the aforementioned creating their own project, NextCloud. There's in depth articles by journalists regarding the exodus, so you should be able to find an in depth explanation as to what occurred and why via google.
Looking at the ownCloud webpage, it is still an active project, however since I haven't stayed up to date on either, I would encourage doing research to determine which one will work best for you.