I wonder about the TUIs consuming less resources. Sure, compared to something like Electron, they will, but on the other hand, pretty much everyone is running a TUI in a graphical terminal - often a terminal with unicode support, utf-8 decoding and antialiasing, sometimes subpixel antialiasing with all that overhead it has. In that environment trying to, e.g., fill a silver rectangular area implies sending all the ANSI escape codes to move the cursor and change the current color, send a ton of characters that represent a "full" block, have the terminal emulator parse all that and then fill the area with lots of tiny rectangles (assuming it does know about the full block character and doesn't just defer to the font engine which does the full block drawing itself using the entire text rendering stack).

In comparison a GUI application would just draw a filled rectangle. For a local X11 application or OpenGL application this may even done as a hardware accelerated operation without even touching any pipes.

To me the "graphical" side of a TUI (which is pretty much most of it) sounds way more heavy than the equivalent of a GUI.

That's an interesting point and I can't really compare that.

But I noticed with an old thinkpad (x220) that I can reduce overall resource consumption and prolong battery life just by switching everything I can to a more terminal-centered workflow.

Ranger consumes less than dolphin, I use NMTUI because i3wm doesn't have a clickable task bar item for configuring WiFi (at least in my setup) and VIM/NVIM consume less than VSCode, IntelliJ, Atom or other editors.

Clearly there is a difference when you compare an electron app to some other running in the JVM or natively but in the end I have the feeling that terminal apps run better and faster.

Another very important thing in my opinion is the possibility to use these apps via SSH which is still my preferred way to remotely use computers (no VNC, RDP, teamviewer etc.).