How to set up two independent home networks so that when connecting their VPN, they do not confuse DHCP?

Question

VPN

There are two home networks (actually more), the keyword is home, each of them has a wifi router (one has a cheap tplink, the other has keenetic giga), both networks must work in a single local network (requires windows network without a domain controller), but depending on the physical location, the gateways for each machine must be different (corresponding to the home network to which they are physically connected).
vpn-connection between networks is not permanent, there was no special need for it all the time, and historically it happened that this is an openvpn client on one machine in one network, and a server dedicated server in another.
the problem is that by dividing the networks into their independent subnets, I didn’t manage to configure the windows network normally (it’s quite possible that the question needs to be reformulated exactly like this - how to configure it to work)
if the networks are topologically placed in a single ip space, then the DHCP servers of the routers begin to respond to requests on a neighboring network, so a machine with DHCP autoconfiguration can get a random gateway from one of the subnets.
How to correctly distinguish between subnets (now everything is written in statics on the same network, but when connected by a laptop and a smartphone that should work on both networks, it is inconvenient to use statics, you have to manually change the settings every time you change location, if on a laptop it is simplified to 1 shortcut per desktop, then with a smartphone is not so easy).

Answer 1

divide ranges and adjust by sets of poppies in each subnet
extinguish one DHCP when a second one appears

Answer 2

Of course, you are a master of explanations, but what do I understand. There is office And with a network, and office B with a network. We need to merge offices.
You must make different subnets in offices A and B, connect them with a VPN tunnel (one more subnet is transport) and configure routing. In order for computers from network A to see computers from network B using NetBIOS (that is, seen in a network environment), you need to install a wins server on network A and network B, and set up replication between them. That's all.
ps under wins server, you can use any computer with windows, but your dhcp server must be able to pass parameter 44 with the wins server address. Or hands hard to prescribe on all computers.