Certainly playing max is the best decision, because the highest payouts you can get for one and two coin play are 2,400 and 4,800 coins. These sums are not small, but you lose the chance to get the progressive constantly accumulating prize when you don't play max.
Except for the sevens you will see three kinds of bar symbols on the reels. The progressive jackpot you will get in a case you hit on the payline red, white and blue seven symbols. The next top payout of 5,000 coins you win when on the reels appear three red sevens and all the other prizes are between 600 coins for three white 7s and 12 coins for three bars of any type.