Is there any literally gold ratio between quality and quantity?!

[Avvy Jones]

I'm AM a newbie to this game and I fall in love with this game. Probably that's apparent by my presence here.

I have this question if it's not obvious from the title: is having eleven 60-70% players any better or worse option than having 7 or 8 45-55% and 3 or 4 80-90% players?

I'm on the level one and percentages are from my point of view.
(I mean, I've seen teams with overall 100-110% quality. Even on the introduction screens, Fire F.C. or with something similar name...)

Oh and is there any significant difference in improvement gain by training between 18 yr old and for ex. 27 yr old?

I must add: If you grasp the idea of having more but little bit inferior players (compared to Excellent and Scout) in squad - experimented and it's viable option, please tell the lower limit of percentage.