I have a Dell laptop that came with a Windows 10 license. It seems reasonable to me that I should be able to run as many Windows 10 VMs as I want as long as I'm the only one using them and others do not access and can not remote into them.

I have been using my full retail Windows 10 Pro for VMs on my Windows 10 Dell laptop. I just use them to isolate customers applications and the different development software and or versions each project needs.

I've done some research and of course Desktop OS VM licensing is complicated and is all but hidden. Most just talk about VMs with a Server OS and that is pretty easy. Buy one Server OS license for upto 16 cores and you can run upto 2 VMs on the same ESXi host.

The desktop VM licensing is a nightmare. You have OEM licenses that it looks like you can not use at all for VMs and then retail licenses that it looks like you can run one VM as long as no one accesses it remotely and then Windows Enterprise licenses that have different functionality and then are you running them on local hardware or on a third party hosting service and is it per device or per user and are use using Windows Software Assurance or Windows VDA subscription and on and on. 

So...

It looks like you can just get a full retail license and run local Windows 10 VMs and just have to mess with the fact that at any moment it will want to reactive as you've change the amount of RAM or CPUs and such. You may also need to buy on for each VM you want to run???

You can get a Windows Software Assurance or Windows VDA subscription for like $600 or so and have to pay each year but can run upto 5 Windows 10 VMs as you have to order 5 licenses minimum???