Took Level 1 at the Javits Center a couple years ago - I think all Level 1 exams in the city are proctored there. Considering that there are easily 3000 people sitting for level 1, probably more, in the Javits Center, it was a pretty smooth process. I can’t remember specifics, but the center is partitioned up into multiple rooms of maybe 500 people per room. I shared a long table with one other person, and didn’t feel crowded despite the large number of people in the room. For the most part, my exam room was completely silent and I was able to focus well. That being said, if you’re easily distracted by shuffling papers/coughing/sniffling, then remember to bring ear plugs. And the test center is cold, so dress appropriately.
Edit: Considering the numbers posted for other centers, I’m clearly, and largely, underestimating the number of people testing at the Javits Center. The point is - the test center is decently well organized, and run fairly efficiently. Most likely, once the exam starts, you’ll forget how many people you’re surrounded by. If you take the exam at the Javits Center, just arrive early and make sure you know where you’re going. It is very crowded and hectic outside the rooms during the minutes prior to the start of the exam.