A Mac will boot and run just fine from ANY external drive that has a bootable copy of the MacOS on it.
Many people have been booting and running like this for years. I started 'way back in the 1980's.
Still doing it today with my late 2012 Mac Mini.
You'll have to get used to having TWO drive icons on your desktop, but that will take you all of a day or two.
I have a hard time understanding why folks get so confused over this issue.
I'll guess that it's not the same over in the "Windows world" … 🙂