回複：what visa will I need to come to US for conference?

After your I-824 is approved, USCIS will deny your I-485 (they will send a denial notice to you), so your AP/EAD will also be invalid and thus, you can not use it any more. Also, it is difficult for you to get a non-immigration visa such as B1/B2 to visit U.S. for meeting because of your immigration intent.