Both Signal and Telegram use SMS for authN tokens, enough said. Being secure and censorship proof while relying on mobile networks just doesn't compute.
Correction: or at least they used to? Now I realize that I am not completely sure.
With Telegram you need a phone number to sign-in and then you can forget about it, and use it just on desktop/laptop. You can set a password as a 2 factor authentication (1st: sms or code to another telegram client 2nd: password).
Bullcrap. Signal works fine on data alone. I have Tasker automatically turn on airplane mode when I'm on WiFi and it's never caused me to miss a Signal message.