If you're using the profile backup option, I presume the backups are being saved outside the Thunderbird profile. As such, there is no dependence whatever on Thunderbird and you do not harm in deleting some. To test a backup, - - exit thunderbird - click windows key and 'r' key - enter command exactly in this syntax:

  thunderbird.exe  -profile  "c:\<profile location>"

I get this. Your Thunderbird profile cannot be loaded. It may be missing or inaccessible.

I am backing up all profile folders and save -always all files is selected. I am saving them to a separate folder I created called Thunderbird backup. There is over 600gb in there and I am running out of space. So I want to delete older backups to gain some space. I assume these are full backups since all profile folders options is selected. I didn't want to delete them before I know for sure it will not delete the message and profile under my user.??? There is another folder under user>name>appdata>roaming>thunderbird>profiles, that is named xxx.default-release. I assume that is my profile there.

Nevermind, I deleted all the old backups and was able to free up 588gb. All profiles and emails are still intact.