There's really just one rule in the basic euchre ruleset I know that you can't break: failing to follow suit. Doing that ends the hand and results in points for your opponent.
You are kinda right about your cards predetermining play though - once you get really good and are playing with other people who are really good, whole rounds can be played in minutes, because everyone just knows what to play.
You think these dumbass neo nazi chucklefucks have enough brain cells to rub together to make that distinction?