I'm using zerotier, but considered both. Any thoughts on comparison between these two? My problem was I needed to be able to connect to a remote Pi on a cell modem that is behind CGNAT. I could not come up with a reasonable solution that used wireguard or ssh tunnels. I tried setting up a tor hidden ssh service like I normally use for remote Pis, but I couldn't get through the cell network inbound to the Pi. @Jay

Sounds above my pay grade. Dunno what CGNAT is, but tailscale could potentially help you make a tunnel to that pi fairly easily.