I think the guy in the video is full of it. The only time I use neg tooth angle is for metals. Sure, most blades will work doing about anything if you want to bull through, but you want the blade for the job. At least the dude got that part right. Don't waste your time using a neg saw blade on wood. Maybe some plastics, I don't know as I don't cut plastic that often. The pros use diamond blades for plastics.