Kouk

If you can find it, the UniFi Switch Lite 8 PoE, should suffice. Even the older UniFi Switch 8 60W will be fine.

OK. Well, if MSRP differs in your area, I guess that will be a determining factor.
 
Even with 20 wireless clients in the same villa (which I don't think villas are set up to accommodate), an AC-Pro isn't necessary.
 
Equating the AC-Pro's 3x3 MU-MIMO to the U6-Lite's 2x2 MU-MIMO isn't necessarily fair. They're 2 different generations, the latter having better optimized hardware/radios.
 
It's not beta anymore. Many manufacturers are releasing WiFi 6-compatible APs because the technology makes WiFi more efficient, especially in high-density scenarios.  WiFi 6E, on the other hand, is a different situation.
 
The U6-Lite and U6-LR have been proven in real-world tests to perform much better than the AC-Pro. Yes, the AC-Pro was a great performer for value at release, but even the nanoHD (a 4x4 AC wave 2 AP) quickly outperformed it. And I have a feeling that, since the U6 is so much better value for performance, Ubiquiti might be phasing out the AC-Pro soon.
 
If you're looking for the 12P to be your router and PoE switch for the APs, the 12P's power output may not be sufficient. Many of these high density APs require 48V passive PoE; the 12P can only provide 24V if I'm not mistaken.
 
What kind of internet speed are you getting from the ISP? Does the ISP provide a modem or gateway device? If it's the latter, can it be easily converted to bridge mode? Do you already have the Mikrotik router?

And the Mikrotik router doesn't support dual-WAN? Check the manual for failover and load-balancing.
 
Why? Unless you buy the Ubiquiti APs in the multi-pack, they should all come with PoE injectors I'm the individual boxes.
 
Furthermore, find the specifications for your particular version of that TP-Link switch to see the PoE voltage supported. The UAP-AC-Pro requires 48V at 0.5A.
 
Unless you're expecting lots of users in a single villa (high density), a UAP-AC-Pro isn't required.
 
A U6-Lite costs less, supports WiFi 6 and performs better despite being a 2x2 device compared to the Pro's 3x3.

It kinda depends if you want to go the Windows or Linux route. If you are running windows as your desktop I would suggest you start by putting heaps of ram and CPU into your desktop and using win10pro to start playing with hyper-v. Run some server installs in VMs and have a play. As a start I would suggest 2x server VMS with ad and 2x client VMS. When you are happy add a freenas into the mix and make it all work.
 
After that look at a build your own PC with as much ram and and CPU as you can afford.
 
It will also help to get a ssd for the VMS to sit on.

It sounds is if you are wanting to do many things with this server. You will want to start looking into Virtualisation, I would suggest ESXi for your Host OS... bit of a learning curve but isint that the point?  From there you can look into a simple Windows (or Linux) OS for your file shares for the NAS element and have a VPN VM set up for accessing it from the Internet. Expect to spend days/weeks on getting things working but thats how you learn.
 
Get yourself a cheap switch (managed) little Netgear 4 port will be fine and connect your server and your PC to it and then the cable from the wall, will work fine. 

For home usage I don't really recommend rack mounted servers as it tends to get very loud.
 
My suggestion for home server is just get a normal PC with good power supply according to your budget, no need to be new.
 
I like to install normal Windows 10 on it so I can use it as normal PC at the same time (I even install GPU on it so I can stream games from it). For any linux/other OS stuff, I install VMware inside it and set it to start on boot.
 
If you need RAID, probably the only safest way is install Linux and use proper software RAID to control it.

Well thats the main part, BECAUSE IT IS FUN! . Just be sure to spec enough RAM if you do decide to go down the VM route. Also make sure (again if you decide to use ESXi) that all the parts you are using are compatible (stick to INTEL NIC's). Avoid prebuilds like Dell C510/610's they are LOUD and expensive to run. Get your feet wet first then move onto greater a bigger things!
 
If you do get majorly stuck just send me a PM, I will get back to you at some point.
 
https://www.amazon.co.uk/Linksys-Business-Desktop-Gigabit-Unmanaged/dp/B00HZMVTBK/ref=pd_day0_147_2?_encoding=UTF8&psc=1&refRID=FGX69HAJ3RHWPNSKA4HQ