The only reason to arrive early if you have baggage is if you mean to check baggage, since you need to give them time to put it on the cart and take it out to trainside. If your baggage is small enough to carry with you on the train, you need not worry too much about arriving too early, since at least in my experience they don't have mountains of Security Theatre. OTOH, I've never ridden on the Northeast Corridor like you are -- the farthest east I've been is Schenectady NY on my trip to Anticipation -- and I don't know what things are like at Penn Station.