I live in the city and the roads here are not to good, my 2019 expedition xlt (normal shocks) drives rough on the bumpy roads. Would the billstein 5100 help with this? Also would the hellwig rear sway bar help with the car moving side to side after riding over bumps?
What diameter wheels do you have? 20in or greater will give you a significantly harsher ride. If you have large wheels I'd start with getting 18in wheels and good tires, which will make a big difference on bumpy roads. If you already have 18in wheels you can try decreasing tire pressure to low-mid 30psi (assuming you're not towing or carrying a load).
The Bilsteins will help with control but they probably won't help much with harshness, and may make it worse. If your suspension is shot and you want a softer ride, stick with OEM dampers.