I’m not so sure what DAV you’re referring to but if you mean the dav:// and webdav:// schemes on Linux, don’t let that confuse you. It’s all WebDAV. I must admit that I don’t know which one is preferred on Linux, maybe someone else can help out. But since it’s all WebDAV, they’re definitely interchangeable.
Yes, Cryptomator for Android is currently in beta. It has been in beta for many months now and is very stable. But still, treat it like a beta. We’re currently preparing the final version so it’s coming out soon™.
WebDAV in Android has nothing to do with how we’re using WebDAV in the desktop version. WebDAV in Android is one protocol the app supports to connect to a cloud storage service (see common URLs). WebDAV in the desktop version is used to provide a virtual drive/filesystem.