OpenZFS native encryption is actually pretty nice and I think it works on Darwin.

I agree with sibling comment that you should look at encfs but note that 1. it needs FUSE and that might be a pain on Darwin, and 2. encfs doesn't protect against certain cloud facing threat models (read the audit yourself, but basically it's weak against an adversary who can see the encrypted data at multiple times).

Veracrypt probably is the answer to the question as you've asked it, but yes the software's background is... weird.

Are you sure you want disk encryption software? Because for "very important documents like keys, etc)" I'd seriously consider just using GPG (or a friendlier wrapper thereof), either for individual files, or tarballs.