I guess the chart shows the power, not the head-heavyness (balance point). Then it all makes sense; I can hit harder with the N80 than with the N50-III, although the N50-III is head-heavier.
I think n55-3 should be further right. I find the frame pretty stiff but maybe the feeling was because I used aerosonic @ 28lbs.
I don't know where you got this information but I can tell you that the bp of the N55-III is definitely higher than 298.
Is the stated BP of N55-3 without string? If it is without, then with string probably around 310 - 315 I guess.
It is dependent on your swing speed and the pronation of the arm when making contact. Since everyone has a different style of swing, one racket may suit another player better than the other racket. I've seen players use the N55-III and really crank the shuttle while some other players hitting just as hard and fast with the N90-III. From an international standpoint the N90-III is used more than the N55-III.
The balance of a Windstorm 300 has a balance point higher than all the N-series rackets however it doesn't mean it will hit harder than them. Every player has a different style of stroke and swing speed so one racket may work better for one player over another. It is always best to have one in hand to try before you buy.
You're absolutely right. The BP sits at 303mm measured from the end of the handle. The specifications can be found in the link below: https://shopbadmintononline.com/badminton-racket-flame-n55-III-purple-p-881.html