Seabra’s Marisqueria would absolutely be my choice, as it:
a) fits your criteria
b) has a crazy selection of seafood
c) it’s where all of the locals eat
I worked in Newark for 10 years and have been going to the Ironbound since I was a kid, and since my Portuguese friends turned me on to it, and it has become my go-to when I don’t want a more upscale feel. That said, Adega is also at the top of my list, but it’s ‘dressier’ in terms of decor (I went there on a date once and they sat us in the queen/king chairs, which was odd since it was only our 2nd/3rd date).
I also love. LOVE. Casa Vasca, but it’s further away from Penn Station. I really think you’ll love Marisqueria–and if you happen to be 1-2 people, I think sitting at the bar is a lot of fun there, too!