There is a difference from Silverthornes game. I do NOT limit attributes to 20. BUT: ANY superhuman ability requires a power modifier. You buy IQ 20? Fine, you are the smartest human alife. You want to buy DX 25? 5 points of those 25 require a power modifier. And to make it worse: I change the % value of some of them (you'll understand the reason after the genre shift). I do allow the following power modifiers:
Biological -10% (careful with continuous abilities)
Elemental -10% (usually limited by the opposite element, discuss this with me please)
If you choose your power modifier, please read carefully what problems you might face. And remember again: ANY superhuman power requires a power modifier. Some do have them included automatically. Like Magery which is automatically "magical" with no reduction. Oh if you miss magical ... anyone wanting to buy a magical ability should also buy Mana Enhancer. All others will need a power modifier for the superhuman part.