Because there's an eternal question, "which player attributes are the best?", I decided to try and answer the question by analysing every attribute range you can get.

 

The study was made on 99 keepers, 99 defenders, 99 midfielders and 99 attackers respectively, in the last week of last season.  All the players were free agents, 17, and Q66. The actual variations might differ by 1 or 2 points, but I believe the amount of players was enough to draw a conclusion.

 

KP: 20-42 (-46-24) 22 variation -35 avg

TK: 20-42 (-46-24) 22 variation -35 avg

PA: 31-57 (-35-9) 26 variation -23 avg

SH: 63-77 (-3+11) 14 variation +4 avg

HE: 61-77 (-5+11) 16 variation +3 avg

SP: 52-78 (-14+12) 26 variation -1 avg

ST: 40-67 (-26+1) 27 variation -12.5 avg

PE: 48-75 (-18+11) 29 variation -3.5 avg

Average Variation per Attribute: 22.750

 

KP: 20-42 (-46-24) 22 variation -35 avg

TK: 45-67 (-21+1) 22 variation -10 avg

PA: 66-82 (+0+16) 16 variation +8 avg

SH: 45-67 (-21+1) 22 variation -10 avg

HE: 41-72 (-25+6) 31 variation -9.5 avg

SP: 48-76 (-18+10) 28 variation -4 avg

ST: 47-82 (-19+16) 35 variation -1.5 avg

PE: 41-82 (-25+16) 41 variation -4.5 avg

Average Variation per Attribute: 27.125

 

KP: 20-42 (-46-24) 22 variation -35 avg

TK: 63-81 (-3+15) 18 variation +6 avg

PA: 42-67 (-24+1) 25 variation -11.5 avg

SH: 30-52 (-36-14) 24 variation -25 avg

HE: 44-77 (-22+11) 33 variation  -5.5 avg

SP: 51-81(-15+15) 30 variation +0 avg

ST: 50-81 (-16+15) 31 variation -0.5 avg

PE: 40-82 (-26+16) 42 variation -5 avg

Average Variation per Attribute: 28.125

 

KP: 61-81 (-5+15) 20 variation +10 avg

TK: 20-43 (-46-23) 23 variation -34.5 avg

PA: 35-61 (-31-5) 26 variation -18 avg

SH: 30-51 (-36-15) 21 variation -20.5 avg

HE: 30-52 (-36-14) 22 variation -20 avg

SP: 44-82 (-22+16) 38 variation -3 avg

ST: 44-77 (-22+11) 33 variation -5.5 avg

PE: 50-82 (-16+16) 32 variation +0 avg

Average Variation per Attribute: 26.875

 

 

To calculate the best possible youth you can get (if all of theme were 5 stars), I put in the maximum values of attributes that don't affect the Q.

Then, I chose the maximum value of attributes that grow Q by 1/11.

Then, I chose the lowest possible main attribute (keeping, tackling, passing or shooting), because it has a great influence on the Q (4/11).

Then, I balanced the rest of main attributes to keep the player quality to 66.

This is what I got:

 

Q 66

KP: 42

TK: 42

PA: 57

SH: 63

HE: 70

SP: 70

ST: 67

PE: 70

 

Q66

KP: 42

TK: 64

PA: 66

SH: 64

HE: 72

SP: 64

ST: 82

PE:  82

 

Q 66

KP: 42

TK: 63

PA: 67

SH: 52

HE: 77

SP: 67

ST: 67

PE: 82

 

Q 66

KP: 61

TK: 43

PA: 61

SH: 57

HE: 52

SP: 82

ST: 77

PE: 61 

 

 

I hope you found this helpful! :D