Have a look at https://forwardemail.net/. It’s a service that handles accepting (and optionally sending) email on your domain, and forwarding any received mail to other backend services, like a gmail account. All you need to do is set some DNS records, like MX and their servers will handle everything. It works fine with domains hosted on cloudflare, and has excellent howto’s to get everything set up and running.

Edit: The great thing about this service, imho, is their guides. They don’t just have a static howto, they template in your information into the exact string you need to copy/paste into the service provider’s web interface. Want to encrypt your plaintext TXT records? There’s a button for that on the guide. Want to learn how to get around a port 25 ISP block, they have a guide for that. Want to set up proper Send-As from Gmail using their SMTP server? There’s a guide for that. :-)

No. USB is not designed to be reliable. It’s designed to be plug and play. Don’t plug and play with your data.

I have always preferred TightVNC over the various other VNC flavours. It does only one thing, but does it well, with minimal setup and network requirements.

I have tried RustDesk recently, and the performance when it worked was nice. But I found it too complex to set up across more than a few machines, and ultimately unreliable, with connections failing without any useful error message, an unresponsive relay, weird certificate errors, etc… It needs a couple of years to mature.

I would suggest looking into using WireGuard to wire your various networks and computers together. It works very well most platforms. You can easily give laptops a road-warrior connection, so they always phone home. Then it doesn’t matter where they are.