I prefer cloudflared myself.
While unbound requests its answers from the authoritative servers for each domain; it does so using regular DNS queries, so it's susceptible to monitoring and modification like any other DNS request. While adding latency by extending that request to several servers, instead of a single trusted provider.
That doesn't really seem beneficial to me. I'd rather use DOH.
This part always confuses me, so I won't be able to give specifics; just a general direction. Most guides explain how to route traffic from a vpn client to the lan of the vpn host. You need to route traffic from the vpn host/lan to a client of the vpn.
You need to change the routing table on the VPS, adding a static route to route traffic heading for your VPNs subnet to the VPN host instead of out the default gateway.
How exactly to do that I'll have to leave to someone else unfortunately. Network config confuses the hell out of me.