I’m an expert at nothing, however, the following is how I understand the relationship between your origin server and Cloudflare Tunnels/Zero Trust services. I stand by to be schooled:

• Traffic between your origin server and Cloudflare’s edge is always encrypted (with outbound only connections via cloudflared daemon). That protects against eaves dropping on the wire between your origin server and Cloudflare.
• Traffic between end users/clients and Cloudflare’s edge is encrypted (via HTTPS/TLS).
• However, Cloidflare acts as a proxy, similar to a reverse proxy. For standard HTTP/HTTPS services. Cloudflare terminates TLS decrypts at their edge to apply features like WAF, DDoS protection, caching, or Zero Trust policies. They then reencrypt and forward the traffic to your origin server. This means Cloudflare can see the plaintext content of your traffic in transit through their network.
• If you expose non-HTTP protocols that are end 2 end encrypted by design (e.g., SSH, RDP, or VPN protocols like WG/OVPN), and you tunnel them thru Cloudflare Tunnel without Cloudflare terminating the encryption, the application slayer data remains encrypted end 2 end. Cloudflare only sees encrypted blobs which they can’t decrypt without the keys.
• Utilizing Tailscale on the origin server creates a mesh VPN using WG. It encryps all traffic directly between devices. P2P when possible, or encrypted relays. Your data is encrypted on the source device and only decrypted on the destination device. Neither Tailscale’s coordination servers nor Cloudflare can decrypt it.

If this is inaccurate, please do EILI5. I’m always down to learn.