I use both older hard drives that have no use in my PC and Google Drive. I tested DropBox but wasn't overly impressed and dropped them within a couple of months.
I don't use the Google Drive app, though - I upload stuff manually. I think their rates are pretty good and I don't upload anything sensitive, so encryption is not required. I decided to use online storage after first a hard drive fill of manuals and so-on went kaputt on my notebook, then my android tablet fried the SD card in it and that was another 32GB of documents up in smoke - literally!
So I collated all the documents again (hope I got them all, anyway) on my laptop and then left it for an afternoon, uploading the entire library. Now the documents are as safe as they can be, and I can refer to them any time, on any of my devices. Very useful for gaming (referring to maps, guides, walkthroughs, checklists for sims etc etc). And furthermore, I couldn't give a rat's ass if they copy the data or publish it elsewhere. Oh - an addeed advantage is being able to use their own editors etc - in things like Google Docs. I can work on documents online that way, without having to have the editor program installed on my PC. Also, I don't know if it's only available for Google account holders or for everyone, but I use their Google Sites for free websites, too - like this:
https://sites.google.com/view/virtual-pilot/home/bae146You can make any kind of website you want, and it costs nuffink.
PS - I forgot, another advantage of Google Drive is that you can share them with anyone. The public, individual people, a group etc etc - and you decide what they can do - view or edit. Same with the websites. I have a large number of docs shared in the flight sim community.