The seat will be the same as standard domestic First, and the meal will be similar, except with two hot options instead of one hot / one cold. You'll also get lounge (United Club only) access at EWR.
Here are threads with pictures of Domestic F meal service:
2019 Let's Eat - United First, United Business, & Premium Transcon Service
2020 Let's Eat - United First, United Business, & Premium Transcon Service