You will get all kinds of opinions. But the simple fact is that if your are within your trucks capabilities you should not need air bags. If you are over your trucks rated capacities then air bags aren't the "legal" answer.
With that said...air bags or other suspension enhancement almost always make the ride more stable and more comfortable.
5th wheel pin weight should be 15%-20%. Toy haulers can have a higher pin weight when not loaded with toys in the garage.
To set up your truck and trailer correctly and ensure you have the best experience do the following...
1) go to a CAT scale (truck stop) and weigh your truck with just you and a full tank of fuel. You will have two numbers, steer axle (front) and drive axle (back).
2) go back to the CAT scale with your your truck and trailer. Make sure the trailer tanks are all empty. Now you have 3 numbers. Steer axle (probably a bit lighter with the trailer), Drive axle (definitely heavier now). Finally, you have your trailer axle.
These numbers are completely made up for this example...
Truck only: Steer = 5000, Drive = 3000
Truck and trailer: Steer = 4900, Drive = 5000, Trailer = 10,000
Your truck weighs 5000+3000= 8000 lbs.
With the trailer your truck now weighs 4900+5000=9900 lbs.
The trailer is transferring 9900-8000=1900 lbs to your truck.
Total trailer weight is 10,000+1900=11,900 lbs.
Now you can generally figure how much weight you can add to your set up. Remember water is about 8.6 lbs per gallon. All your clothes, bedding, food... Add all the people in your truck, the dog, coolers...
You want to check the max GVWR for your truck and make sure your truck doesn't go over that number when towing. F350 non-dually GVWR is somewhere around 11,900 lbs (don't quote me on that). Check your door jamb sticker.
In my example above with random numbers the pin weight (or hitch weight) is too light at only 10% of the trailer weight. This would be about perfect for a bumper pull but a 5th wheel should be 15%-20%.
If this seems complicated...it's really not once you get it. Just go line by line in my example and use your actual numbers. Getting weighed at a CAT scale is about $12 or so.
I get weighed a few times a year "for fun" when passing a scale just to see where I am at with weight when loaded up in different camping "configurations".