If the laptop supports dual drives (not unheard of but not the norm) it’s way safer to dual boot from different physical drives.
Whatever OS you choose make sure they have a guide for dual-booting. Any Linux OS should be capable of dual-boot but not all will support that configuration equally.
As a failsafe I would also make a rescue USB, especially SystemRescue because of the findroot option.
If this is indeed a security feature I’m about to buy my first iPhone.