CnCNet client is internet, hurr durr.
I doubt there's any way to do pure LAN with Windows 10. With Windows 7, yes, but it isn't easy if you're not a computer scientist. Your best bet is CnCNet (with the hack of using VPNs) or some other online service/server. I'd go as far as recommending GameRanger to you which I have never recommended to anyone under any circumstances but for you it sounds like the best idea.
There's things like VMware. But again, don't bother unless you're a computer scientist and have access to a super high end server with a minimum of 8 physical cores and at least 32 GB of RAM.
These things are generally not worth it. Windows 10 is troublesome enough.