-The fee is the same, not different.
2)由于postdoc的薪水很低,在申请H1B的时候,还会不会像申请公司H1B时候对薪水有“高于本地prevailing salary”那样的要求?
-Yes, it still applys to the prevail salary, but this prevail salary is based on your postdoc position code, not based on your original company job code. So, it should not have a problem.