Yes, you get to know instantly. They will keep your passport for stamping if its approved.
I dont think it matters "much" who is taking the interview. IMO Visa type and its relevant documentation is much more important. I remember during one of the interviews, there were back to back 6-7 rejections on the window I was supposed to go to(I know they were rejected because they were going back with passports in their hands), but when I reached there, the guy dint ask much at all and the interview was over within a minute. But be very careful while filling DS-160 form and check the documentations required. I was grilled for a good 15-20 mins for a small mistake in DS160, which I dint even realise while filling it.
You should receive your passport within a week or so after stamping.
All the best!!