Congrats! It has been a while since I have seen empty seats in First so I would say you lucked out.

Weight and balance are a bigger issue on the smaller planes. Choosing a seat in the back will only get you a noisy seat in most cases.

The best advice I could give you would be to check in on the kiosks. This will let you check all of the seats available and maybe get a better seat for yourself that day. You can do the same thing online before the flight.

If you do get a back seat, I suggest noise-cancelling headphones.

Happy Travels!