(Incremental) backups safe for system disks?

Making an (Incremental) backup with the bootdisk is safe because Windows isn't running. But it's also a very time consuming way of backupping.

Paragon can also do scheduled backups using a program running in Windows.
I'm wondering how safe/exact those backups are. Windows and installed programs keep writing to disk all the time. Windows locks and deletes files, etc etc.

How does Paragon guarantee an exact snapshot?

Depending on what product you are using, if you have Settings>Backup Options, check Hot Processing which uses Microsoft's VSS Technology. Several years ago I needed to reinstall/rebuild Windows but needed my PC daily so I'd backup, work on the reinstall/rebuild, restore, backup, etc. for about five days. Also when I was the W10TP I restored it probably 10-15 times without any issues.