This should help with YT... https://lumen5.com/learn/youtube-video-dimension-and-size/
It's a balance between desired quality and ease of editing. Lower res and smaller files make editing easier, and that goes for any NLE.
When constructing your project, routinely Save Project Files AS, so as to not overwrite prior saves. Save Project Files will overwrite. Then you're protected.
Launching a VPJ (non-playable control file) will load the project just as it was when the save was made provided no files have been deleted or moved.
If you make a mistake during editing immediately press <ctrl-Z> (EDIT | UNDO) to backtrack step-by-step.