Should virtualize within MacOS or use a Hypervisor like VMWARE ESXi I have a Mac Mini late 2012, 16GB ram with 500GB disk, multiple (3) gigabit NICs, and some external USB3.0 drives. 

My requirements for guest OS are:


One Macos High Sierra with Server.app
One pfSense linux guest (requirements are minuscule.  CPU 600MHz, 512MB RAM, and 4GB HDD)
Maybe a second Linux instance to tool around with - No windows guest VM


My research shows I don't need to use ESXi but it has a lot of features  I'd like to leverage, snapshots, Multiple test configurations and etc. Given that nothing else is running in the ESXi environment. 

(the goal of knowing how to measure this lets me weigh if I upgrade to an SSD and or even bother to install ESXi)

I'll be using the ESXi6.7

Spec of the hardware, 16Gb Ram 500GB HDD or SSD

In your experience, how much (CPU/RAM) overhead would the virtualization layer add?
Decided to go with VMware, more an industry standard.  Looking into my own question, the overhead for VMware outweighs the the benefits.  I put it at about 15-20% on CPU &amp; RAM.  This is from research, not empirical data.  I have several devices/servers I want to build, none are resource intensive. I upped the Mac Mini to 16gb Ram 1TB SSD and 2TB SSHD.  The max it can take for less than $200.  Should be plenty powerful.

Some context... 
This is more of a home project.  A server to store family's media, documents, and backups (mostly macs &amp; iOS).  I'll also build a full featured network firewall, I don't like black box or desktop firewalls.  I like to know what's going on.  Lastly a home automation server, there are some integrations between devices/protocols that require a system in the middle. 

I used to be an Windows engineer, 20+ years ago, when that was a new thing.  Since then moved on to management.  I try to stay close to the technology, but virtualization (hand's on is new to me).  Tired of the planning and managing tech.  I'm not allow to touch anything anymore.   I have to use my own desktop teams for my work machine. I want to get my hands back on.  Hence this home project.  though a home project, it seriuos for me, I like to research and understand best practices.  Not to mention the geek out factor. :-)

Look forward to learning here and other sites.  Who know, this "old man" (not talking punch cards or anything, may be able to answer some questions.

Thank for your help.

Sunil