800 dry pounds would be the max I recommend for your receiver. That will go up. If you have already adjusted for dry to loaded by adding 200-ish pounds, great! Also keep in mind the payload of your truck. Some F150s do not even have 1000 pounds of payload! Make sure yours has enough for family in the cab, 200 pounds of cargo in the bed, and trailer tongue weight.
I thought round bars offered more clearance? I wouldn't worry about one style over the other as much as getting integrated sway control vs. friction bars. Reese Straight Line, Equal-i-zer, and Blueox Swaypro are all good near the same price point. 1000-pound bars seems appropriate for 600-1000 pounds of loaded TW.