You are probably aware that the System Vol folder is used to keep Restore Points, and some security features. Certainly, if you have a space problem, it is irritating.
If you have not, already, open the Control Panel (legacy) - System - System Protection, and disable all the restore points on your computer, unless, of course, you feel a need for them. .I use image backups so do not have that need. I think you will find this will reduce the size of the folder considerably, after a reboot.
You can also take possession by changing security settings. This is something to be taken with the utmost care, as it is locked off with intent. I do this routinely on a new installation. I am not recommending. This is mine, as an example...