回複：NIW and EB11 do not need

No matter which catagory you are filing, it will be safer to have a job offer (verified by employment letter) if YOU ARE INSIDE THE U.S.!!!
Think about it, if you don't have a job offer, what are you doing in the U.S.? why the INS issues you a GC? That's because your are contributing to the U.S., again, no matter which catagory you are filing! If you are not in the U.S.(e.g. currently you are in China), the only catagory you can file is AEA (Alien With Extraordinary Ability). For NIW, even if you have filled out ETA-750B, you still need to have an employment letter (otherwise how can you claim that you are benefitting the U.S. interests, and you are qualified for a "National Interest Waiver"? EB-1/OP or OR is purely employer sponsored petition, it is a must you have employment letter. For AEA, you don't need ETA-750B, but it is still helpful (although not a must) to include an employment letter, because you can still emphasize the critical role you are playing in your current work while you are petitioning.