Hi Melissaash
Superturbos are fun but as Tulabas mentioned, because you are in push or fold mode from the start, the variance is huge; so you need a very big sample before you can find your true winrate. Important thing about them is to know ICM.
@rakeback in FR: It is quite hard to say because the rakeback is calculated on the weight contributed rake meaning that it is based on the rake from the amount you contributed to the pot. So it is different for every one depending on their playing style. the best is to give it a try. BUt remember Winrate is more important that rakeback. Rakeback is just a nice little addition /topup at the end of the week 
Best regards
Thazar