Safely installing viruses on a virtual machine?

[NoPuhi]

I stumbled upon a website that provides a free download to a piece of software that im 90% convinced it is actually a virus.
Since it got my attention, i have the urge to test it out.
I installed a Oracle VM Virtualbox to act as a sandbox containment for the virus so it does not cause damage to my host machine and the system and files it contains.
I taught i was all set but then it asked me if i would like to create a virtual hard drive and which type i would like it to be. I have no idea which would be the most secure option so i taught to ask here for advice.
Id like some information on how to set up my virtual machine as secure as possible so there would be minimal to none leakage.
I have already set up a system restore point and am running Avira anti virus and Malwarebytes anti malware.

 

[USAFRet]

Some viruses can detect and escape a Virtual Machine. Thereby infecting the host.
The only real safe way is a whole other PC, airgapped.

And don't rely on a Restore Point. Those can become infected as well.
Instead, create a full disk image, and have that saved elsewhere and offline.