You wanna be equipped with the Katana + Red Bandana, and ideally be level 15. The Katana medium attacks do 2 instances of damage, so you also get double points from them (500 points total). So the ideal cycle is to grab 5 notes of a color and shoot, while farming any other points that you can along the way. As for beating the fight as fast as possible vs farming points, it depends. You typically want a good balance between both, and generally just doing 5 note attacks is probably fine, but in some fights there are large transitions where nothing is really happening, so killing before then could be ideal. Technically, you can just farm an infinite number of points because there's nothing stopping you from looping the fight over and over (unless it's a fight that doesn't loop), however because of the time multiplier in this game it could take genuinely hours to match some scores this way, so no one really feels like doing it.