How much free space should I left in a Veracrypt container

How much free space or percent of free space should I left in a Standart encrypted file container? Is fulling it completely a dangerous thing to do? I got a worry of "what if this doesn't open when I need it" when I see 300 kb left in a container. Because windows also places it's recycle bin and system volume information there I would be already created the volume.

Also I need any advices on not to lose data. When I need a backup 1 year later is there any chance that the backup becomes corrupted until then?

Also a question not about Veracrypt maybe: Any harm in compressing files with .7z or .rar? I'm putting these compressed archives in the Veracrypt container. Any harm doing this? Is compressed data more prone to corrupt? Need your thoughts.

Thanks

Not a power user, but anyway...

As a mounted file-container looks and behaves like a regular drive, the same issues apply filling up a file-container as with any drive -- it is an operating system management issue. From habit, I try not to fill a drive as I prefer to copy the data to another higher capacity drive (or file-container) because I am sure to need more drive space anytime soon. That is my determining factor -- not the percentage amount of free space available, but how soon I am likely to need more space.

The important thing for backup security is the number of backups and the frequency of the backups. I would not rely on a single backup over a 12 month period whether a file-container or not.

Compressing files makes no difference to the integrity of the data (all things being equal) as the file-container behaves as a regular drive. File corruption is more often hardware related, like a drive having disc sector issues or failing from wear and tear. As for the data loss risk in using encryption, file-containers are safest option for new users.

But having lots of backups is really the safest bet, rather than trying to better manage one or two file-container backups.

Is it normal for a container using Argon2 (default settings) to mount about 7 times faster than a container using SHA-512 PBKDF2 (default settings)? I thought Argon was supposed to be slower.