Naturally, some uploaded tactics that takes advantage of the flaws of the ME will perform better than the others but if even then, there is no best tactic. If your best players are wingers, then a formation using wingers will be good. If you have no wingers at all, well then the uploaded tactics using wingers are rather useless.
As for differences between playing with a top team and in the lower leagues, well then the first step is to recognize that you are in fact playing with a weak team full of really, really limited players. You have to accept that your defenders will make easy mistakes, that your forwards will miss sitters and that your players wont be as mentally strong as the players at the highest level.
Normally I close these kind of threads directly as they against the postingrules but as I think that this thread could sreve more people than you, I will close this one and open up a new one on the same subject with a different OP and a different name