Advice for long 5+ hour rides

Hey everyone I am planning to do some long indoor rides on zwift to get a feel for what long rides feel like in the safety of my home. I have been training inside and outside for longer rides and want to use zwift as a way to get an idea of how my body reacts to the saddle, fueling, and overall time on the bike. I live in Florida and they recently connected the east and west coast with a 250 mile bike path that I would like to take on at some point.

My question is simple. Are there certain settings that will allow me to ride these longer durations without as much resistance when I encounter steep inclines or mountains? Hardware settings, custom workouts, or free ride settings? The goal (if possible) is to make the resistance as light as possible so I can focus on how my body reacts to being on the bike for what I consider long rides of 5+ hours. I figured on these longer rides I would try and get some of the route badges along the way. Any advice would be helpful.