Do I need to erase the disk before restoring from time machine backup disk ?

Hi there,

I have a late 2012 mac mini running Mojave 10.14.6 (18G103).

Last time I tried to install the latest security update, process stuck and it failed to install the security update and the computer was never able to boot again. It was displaying a black screen when I tried to restart the computer and that was it. Unfortunately, I didn't get a time machine backup at the time and I had to install the OS all from scratch by erasing the disk.

Now I want to give it a try again. But this time I will be backing up the whole OS on an FW 400 external drive which is WD My Book, in case of any failure without having to reinstall the whole OS from scratch.

When I want to do a clean install of Mojave, I boot from an external usb flash drive with the OS in it, erase the disk from disk utility first, then install the OS from the usb drive.

So let's say that the security update failed once again and I needed to restore from a time machine backup.

My question is, do I need to erase the disk before restoring from a time machine backup, just like I do during a clean install ? Will time machine wipe the whole system drive and then restore the backup by itself ?