On which variables does the result depend?

[Juanxito]

I mean, do any of these things matter, for example?:

• If the opponent has a good attacker on the right, then I should put my best defender on his side?

• If I use Wing Play, should I put the best players on the sides?

• If I make the Side Defenders attack, is it better if they have more Attacking points?

• Do countries matter for better play between the players? Does anything else count?

What else matters?
Thanks!

[DMFArranhado98]

If the opponent has a good attacker on the right, then I should put my best defender on his side?

I act according to this, yes.
Even if this doesn't happen to be true, IDK what else we can consider while lining up our players.

If I use Wing Play, should I put the best players on the sides?

Playing through Wing Play should feature forwards with higher DEF on the wings and not actually with higher ATA.
At least, you'll notice that pattern when comparing Strikers IRL's DEF to Wingers IRL's same stat on OSM: wingers have higher DEF than strikers do.

If I make the Side Defenders attack, is it better if they have more Attacking points?

I always line up defenders with higher ATA on the wings - regardless of if I play with upcoming backs or not.

Do countries matter for better play between the players? Does anything else count?

Yes. There's a nationality bonus for team performance.
Although, I neglect it (otherwise, that'd make my squad building harder), so I'm not even sure how it works. I think it requires squads to feature, at least, five players with the same nationality on the starter XI.

[Manager PR 9]

this is correct. thanks