-The fee is the same, not different.
2)由於postdoc的薪水很低,在申請H1B的時候,還會不會像申請公司H1B時候對薪水有“高於本地prevailing salary”那樣的要求?
-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.