My advice:
Store your works locally (if you need a word processor, LibreOffice is good), and have a cloud backup solution for disaster recovery. (I use Backblaze, but there are many other options; you'll probably want one where you can set an encryption key so that even the backup service won't be able to read your files)
Then, regularly test your backups; go into the dashboard, check that the files you care about most are listed there, download them and check that the downloaded versions are what you expect.
Once that's in place, work out what (if any) cloud document or file sharing services you want to use for easy access between devices if you need it. For a Google Docs replacement, I'd recommend cryptpad.fr. If you want to just share the files between devices, I haven't heard of any issues with Dropbox (yet).
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