Advice needed creating Tactics / Positions

If this post is in the wrong forum, Sorry, but I thought this would be the correct one. 

Sorry again for any mistakes / grammar or typing, as Endlish is not my first language. 

I have to admit, that for the last few FM's I always ended up using downloaded Tactics. But I want to start creating my own, and now got to a point, where I am wondering about positions. 

What position goes well with it's counter part. 

Often times, Players on the left, and the right side use different roles, and I can't bring my head around why? 

Wouldn't I want the tactic to work from both sides? for example crosses:

if Left wing player is a Winger, and right wing player is inverted Attacker, don't they perform different? 

If I play with 2 Strikers and 1 AM, what positions play well with each other? 

Is there a Guideline, a website where I find those Infos? 

Best Regards, and Thanks in Advance.