Swingweight is a very personal issue and there is no black and white here. You need to find your personal "cues" as too when a racquets's sw is too high or too low...
Too high: hard to snap through serves, late a lot on groundstrokes, get tired prematurely in long matches, late on overheads.
Too light: Have to swing faster than comfortable with, too easy to yank racquet off course, no plowthru, lots of twisting on slight mishits, timing is harder.
But yes I agree PP...it IS the most important racquet spec for sure.