In windows you may need to add an ifilter. Adobe’s is pretty good. Then windows search will be able to search contents.

The answer here is still a single vpn, and Tailscale makes this even easier.

What you’re describing is overly complex routing, and split DNS.

Join all clients to a single network.

From the diagram you just want to put everything within a vpn so they are on the same network.

You can choose whatever vpn solution you want but I like Tailscale since you don’t need to set up any inbound nat or firewall.

From the diagram it looks like you want your outside clients to use vpn as well.

Yes.

Otherwise, just open up ports on your network firewall and set up DNS to point to your external ip.

There might be a way to do this with cloudfare that is more secure.

Edit: you might want to create a network diagram to help explain what you have and what you want to do. The way you describe the problem is confusing.

Install Tailscale on your vps and your homelab server.

Share the Tailscale dns of your server with guests.

Use your vps as your exit node.