Unreal Engine's built in networking systems are suitable for 64 players, maybe 128 tops. It's replaceable, but I wouldn't recommend delving into that.
I will say this though, if you have 1 C++ programmer with UE4, they can create functionality not builtin to the engine and expose it via Blueprint (the visual scripting language) for non-programmers to use. Blueprint is a fantastic and very easy to use tool. Take a look at the forums to see the incredible things people have built with ZERO programming knowledge.
And talking about Blueprint code is done through screenshots https://forums.unrealengine.com/showthread.php?60637-Unable-... I guess there is still no auto generated text representation you could copy paste.
https://mono-ue.github.io/about.html
If you want to code in C# it is the primary language for Unity, and a commercial third party unsupported add on for UE4.
I recommend everyone interested in the two try both. I personally prefer Unreal Engine, but everyone is different.
Unreal Engine is also moving quite quickly, adding new features, marketplace content, improving the UI, etc.