Thank you! I use raycasts to determine the length, then a Line2D node for rendering the beam. By setting the scaling mode (in project settings) to viewport and using a low resultion the beam gets pixelated automatically!
For the adaptive terrain I used tilemaps with the autotilling/terrain system. Creating the art for the tileset can take a lot of time but I've made my own tool for speeding up that process significally.
But in short, the things you're asking about are all more or less built into Godot.