The ETC has a bunch of different MIDI functionality which means you can program the visuals to change in different ways in time with the music - including changing the mode (pattern), background and foreground colours, etc. This is especially good for electronic sets where everything is locked to a set tempo.
For playing the ETC in your setup, you don’t need to worry about MIDI - you’d just want to select a mode which reacted to the input from your guitar. There are different ones available that will display the audio as a waveform, or in different interesting ways. There’s also a footswitch input that you could connect up an expression pedal to (I can’t remember the spec you’d need, but it’s in the manual) and get more control over the visuals that way.