NextCloud and how great it has become

OH I completely forget to actually answer your question :)

To install NC, first you need a linux machine (I would prefer UBUNTU for NC), then you should install the required components such as PHP, MySQL and so on and finally the NC itself. Maximum it will take about 20-40min depending on your Linux knowledge.
 
The 3rd option looks most appealing, as I do not have access to a dedicated Linux machine.

Can Windows Subsystem for Linux (WSL) for Windows 10 be used for anything, or not recommended?
 
The 3rd option looks most appealing, as I do not have access to a dedicated Linux machine.

Can Windows Subsystem for Linux (WSL) for Windows 10 be used for anything, or not recommended?
The answer is YES however, I strongly would not recommend it.

PHP in general is a native feature of Linux machines and always PHP scrips run better on Linux. BUT... you are always free to test.

I unfortunately do not have enough experience with Windows Servers that I can help you. I am even running Linux on my notebook and desktop machines :)