Hi, kinda basic answear, but I like to use OneDrive. It's easy to setup and works everywhere I need (windows, android, linux). I have stuff like KeePass db on there and it works like a charm. As for backups, if it's something really important/secret, separate drive looks like the best solution for/to me. Nothing fancy. Althought, some people I know, use next cloud and it looks really nice, never made time to set it up.