The install process is as easy as it could be for a debian based distribution. I don't need to walk through it because there is plenty of youtube videos i can refer to. And Documentation of univention is fantastic. So go on and read a little bit [ univention: https://docs.software-univention.de/quickstart-en-4.3.html ].
The nice thing on linux is "headless" operating! While most Windows admins do not install windows without GUI - WINDOWS needs a lot of RAM to operate smooth. The next thing is that all server services are bloated and function overloaded - I call it all features on policy - which is not easy to debug!
Linux on the other hand can operate with less then 512mb RAM stable and smooth. When it comes to virtualization RAM matters because all client-hosts on a hypervisor do share their components with each other installed virtual machine.
For sure the single machine setup without virtualization is best practice. Operating system on a fast SSD and DATA storage on cheap and slower disks is commonly used. Data Security is the most expensive part of this settings because you need every device in rendundancy - so the costs double! In this case virtualization is cheaper.
The Synology® DiskStation with 2 bays is a cheap solution for raid 1 setup. The raid implementation is software raid so in my opinion it is better to have a 2bay with big DATADISKS than having a 4 or 8 bay Diskstation. Software raid is quite CPU intensive and as more DISK you drive as more resources are booked by the system itself.
The DS218+ is based on a x86 cpu (Atom) and you can add some additional RAM to host another virtual machine on it. That's our setup our virtual machine holds the active directory server, and the DSM itself provides the SMB storage.