Not the GP, but I also use Hetzner, but use Tailscale to connect securely across different Hetzner regions (and indeed other VPS providers).

Hetzner does provide free Private Networks, but they only work within a single region - I'm not aware of them providing anything (yet) to securely connect between regions.

No, I use vpncloud for a local (within a datacenter) VPN. This lets me move more configuration into ansible (out of the provider's web interfaces), avoid additional fees, and have the same setup usable for any hosting provider, including virtual clouds. Very flexible.