Which is more susceptible to an EMP, an SSD or an HDD?

No, no, no!!!

• Public access to services like a website: Cloudflare Tunnel
• Restricted access to just a few users: Cloudflare Tunnel + Cloudflare Application
• Exclusive restricted access the infrastructure: Tailscale

This is my policy: For publicly accessible services like a website, I use a cloudflare tunnel. For restricted access to just a few users, I use a cloudflare tunnel and a cloudflare application to manage access authentication. For my exclusive restricted access to the infrastructure, I used tailscale.

Good God, man! On the one hand, I think you are absolutely insane. But on the other, I am completely envious. Rock on!

It really comes down to what you are trying to accomplish. I used it for a while also. It is very friendly and it provides many good features and apps to work with. Ultimately, I found it to be limiting, so I switched to Proxmox VE and just created several VMs and LXC Containers to use for various purposes including Docker.