421 is where I sat for my first Yankees game at the new ballpark. This was last season. I live in south Jersey in Phillies territory, so I don't get to make it to New York too often.
Most comfortable seats I've ever had on the upper deck of an MLB ballpark. They're not the hard plastic kind, they've got a little bit of cushion.
My knees were also not touching the row in front of me and there were no fans on either side of me to make me feel cramped up. The upper level at Yankee Stadium was much less forgiving in terms of space in all dimensions.

NYY Steak is the steakhouse on site. Steaks are all $30+ so it's likely not on the agenda for most fans. There is, however, a Hard Rock Café near Gate 6 that usually has strong crowds the day of the game.
Gates open two hours before the first pitch so if you want to see all of the monuments of former Yankees great in center field, you should get there right when the gates open. Line up outside of Gate 8 in center field to get in line the quickest.