It is strongly recommend to create bootable rescue media immediately after the first backup; if the operating system crashes, the only way to restore it from Acronis True Image 2019 backup is restoring from the bootable media.
If your Mac includes the Apple T2 chip then you need to modify Secure Boot settings in order to boot from Acronis Bootable Rescue Media: see Acronis True Image 2019 on Mac: Changing startup options on Apple T2 chip
Follow these instructions to create a bootable media:
It is recommended that you create a new rescue media every time you upgrade your Mac OS X to a newer version. Otherwise, your rescue media may not work properly.