Reddit mentions of Protectli Vault 4 Port, Firewall Micro Appliance/Mini PC - Intel Quad Core, AES-NI, 4GB RAM, 32GB mSATA SSD

Not gonna poop on your parade since this sounds like a learning opportunity.

But.

You could've gone with something like this https://www.amazon.com/Firewall-Micro-Appliance-Gigabit-AES-NI/dp/B0742P83HY/ref=mp_s_a_1_3?keywords=pfsense&qid=1565650952&s=gateway&sr=8-3 and it's cheaper, fanless, draws less power and has aes-ni support.

I explored building but went with this box instead and it has been flawless, openvpn, etc in a 40 person enviroment. https://www.amazon.com/Firewall-Micro-Appliance-Gigabit-AES-NI/dp/B0742P83HY/ref=lp_14854310011_1_1?srs=14854310011&ie=UTF8&qid=1537190260&sr=8-1

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pfsense on a netgate or similar.

This one will handle multiple VPN connections much better because it has AES-NI:
https://www.amazon.com/Firewall-Micro-Appliance-Gigabit-AES-NI/dp/B0742P83HY

If you aren't doing much encryption (VPN Traffic) you can save a little money (this is the box that I use at home):
https://www.amazon.com/Firewall-micro-appliance-Gigabit-Intel/dp/B01AJEJG1A

I recently switched from SonicWall to OPNsense. I'm running VPN and some intrusion detection on a little Protectli box. It's worked very well. The link is for the one I'm using, but there are barebones ones available as well.

Amazon

Specs:
Intel Quad Core Atom E3845, 64 bit, 1.9GHz, 2MB L2 Cache, AES-NI hardware support
4x Intel Gigabit Ethernet NIC ports
4GB DDR3L RAM, 32GB mSATA SSD
1x USB 2.0, 1x USB 3.0, 1x RJ-45 COM, 1x VGA
Solid State, Fanless Silent Operation, Compatible with many Open Source Software distributions

I got this one for an untangle box: Firewall Micro Appliance With 4x Intel Gigabit Ports, Intel Atom E3845, AES-NI, 4GB RAM, 32GB mSATA https://www.amazon.com/dp/B0742P83HY/ref=cm_sw_r_cp_apa_VyoXAb31HR6M0

Works great so far! :)

Yes. You can download the source code and build it yourself if you want, and you can use the resulting build in production or to test that it's the same as the binary files on pfsense.org.

However if you are going to sell or distribute pfSense software or your own hardware devices with pfSense loaded on them, whether you build it yourself or download precompiled binaries, you have to remove the pfSense trademarks.

There are a number of companies that sell 'pfSense' routers now, but without distributing the software. Here's an example that comes up in an Amazon search for pfSense... "The Vault has been tested with many of the most popular open source software firewall solutions. Compatibility includes pfSense CE, VyOS, OPNsense, Security Onion, Untangle, CentOS 7, *BSD, Linux, Windows and others.". The box is shipped blank without any OS installed but their support will talk you through downloading and installing pfSense yourself if you can't figure it out.
In this case they are not using the term pfSense as part of their product name or feature set, but rather as a description that the product is compatible with pfSense should you choose to load it.

Sorry for coming off strong -- probably posted at the end of a long day.

Yes, you want a VPN for local access, and not port forwarding. Yes you *can* run the VPN on your server, but it is better to run it on the edge device (so you aren't exposing your server directly to the Internet). I use one of these, with pfSense, as my firewall. It runs OpenVPN great. https://www.amazon.com/Firewall-Micro-Appliance-Gigabit-AES-NI/dp/B0742P83HY/ref=sr_1_3?keywords=protectli&qid=1564195635&s=gateway&sr=8-3

If you are comfortable with Windows I'd recommend running Hyper-V over ESXi. TBH I don't think ESXi really shows its value until you are using some of the higher end vSphere stuff. Hyper-V will run on Win 10 Pro so you don't technically need to shell out for a server SKU.

You can then throw whatever you want on top -- some Windows, some Linux (probably better for some of the tech you posted).

As far as hardware goes I like my home equipment quiet and energy efficient. I quite like the Supermicro Xeon-D and EPYC 3000 mini-itx boards. They pack a huge punch for the space/power/noise and IMO the up-front cost is well worth it.