what is the best rush strat on GOW?

There is no best, it's all relative to many factors in the game.

archers can go lvl 7 and grunts can only go lvl 5 so repair your mill and go attack him with your archers. remember to patrol.

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Mage Guild

ok then what is the best for ef and high resources, in a 2v2 match?

Just do a 1 rax rush(rep rax and smith if ur 12/2) and scout your oppenants and once u find them; decide based on what they are doing what lvl u need to go and if u need another rax...
If they have two raxes u might wanna make antoher rax and outrush them or u might wanna stay one rax and go high levels and stay defensive with lots of peons....
whatever the best way to go is to adapt in my opinion