Can confirm. I have used one or the other exclusively for 20 years. Mostly on laptops. And these days with just a tiling window manager and terminal.

It just works.

Another option: encrypt a sparse file rather than a disk volume. Mount the file to local filesystem and open and close it there.

Fair enough!

So you would suggest to get bigger and bigger storages?

Personally I would suggest never recording video. We did fine without it for aeons and photos are plenty good enough. If you can still to this rule you will never have a single problem of bandwidth or storage ever again. Of course I understand that this is an outrageous and unthinkable idea for many people these days, but that is my suggestion.

The local-plus-remote strategy is fine for any real-world scenario. Make sure that at least one of the replicas is a one-way backup (i.e., no possibility of mirroring a deletion). That way you can increment it with zero risk.

And now for some philosophy. Your files are important, sure, but ask yourself how many times you have actually looked at them in the last year or decade. There’s a good chance it’s zero. Everything in the world will disappear and be forgotten, including your files and indeed you. If the worst happens and you lose it all, you will likely get over it just fine and move on. Personally, this rather obvious realization has helped me to stress less about backup strategy.

By definition an email server is not under your control, so the question of whether or not it runs FOSS is a bit moot and in any case impossible to verify.

In terms of privacy-respecting email hosting, Proton, Posteo, and Mailbox all spring to mind.