Major options :
A- Set up to boot from GPT partition
B- One OS to run VMs (hypervisor type 2)
C- Hypervisor type 1
D- Live OS
Option A
Pros : More power, less energy consumption, no need to split CPU and GPU resources. A partition with user data can be shared between OSes.
Cons : Every time a new OS is installed, it put at risk the full disk config if the user do a mistake. It's better to keep partitions sizes. FDE it's difficult to apply or need to trust OPAL SSD.
Option B
Pros : Easier to set up. Easy to delete one VM. Ability to use secure boot and TPM (maybe Pluton one day)
FDE at least from the main OS. A VM compromised could retain most malware from going to the host OS.
Cons : CPU and GPU resources are reduced for the VM. To share data with the host or other OS is not very convenient. The virtualization software need to fake the hardware. Need to trust the main OS for others OSes. Emulators could refuse to start on the VM.
Option C
Pros : Nearly all resources available to the OSes
Cons : more technical to set up, less common for personal users.
Systems Proxmox, Qubes, Xen
Option D
Pros : Good to try a new OS, or in mobility way.
Immutable if booted from DVD-R, CD-R.
Cons : Slow disk access. Not convenient for every day use.