Grew up there and still visit family there multiple times per week:

• yes it's mostly residential. The commercial area (mostly Central Ave, although lately Palisade Ave has some new bars and eateries) has most of what you'd need without needing to own a car (supermarket, fruit stores, restaurants, fast food)

• about owning a car: unless your new place has parking, don't bring a car. It's annoying to find parking after 6pm. And if you park too close to the corners you'll get a ticket

• the morning bus / jitney along JFK Blvd to nyc is slow but dependable. Most days I'd budget about 40 mins into port authority (if you get on near the southern part of the Heights, less if you live farther north). There's other buses on Central Avenue but they're not reliable at all - in the past buses would not show up or would come 2 at a time, or were otherwise too full and wouldn't stop.

• living withing walking distance of the path is preferable, but you probably wouldn't save much time vs jitney (20 min walk to station, couple minutes to get downstairs, 15 min ride etc).

• crime isn't much of an issue. But as in any city it will exist. Just be careful and don't walk around buried in your cell phone late at night. Honestly the worst crime is getting your car's catalytic converter stolen (all the more reason to not bring your car).

• nightlife is limited. The restaurants and bars in the Heights are no frills, but aside from a handful (Renatos, Corto, maybe lo fi), the rest are more of "to go" eateries. Hoboken is a 10 min Uber ride away from the Heights and will be a much better option for Fri night/ date night, but for regular eating the food in the Heights is top notch (in terms of variety and taste)