Most probably you were either using too little arimidex, or it was fake. In any case, it is much better to use aromasin, as it is a much better aromatase inhibitor. It is a suicide inhibitor, so there will be no estrogen rebound with it, it will improve lipid levels, and bring along many more benefits not seen with arimidex.
You have heard wrong, because no matter the ester attached to a steroid, it will still retain its main properties. The only thing that will change with the ester, is the release rate - nothing else. Therefore, testosterone propionate will also aromatize, and it will also cause water retention. The only two things that will be different, is that it will start acting faster, and it will give more painful injections. Just use a proper AI, such as aromasin (10 mgs EOD from the first day of the cycle), and you will be perfectly fine.