Welcome to the "Roo Kroo"!!
from a fellow firefighter/EMT!
you should look at either the Equal-i-zer WDH or the Reese Dual-Cam WDH. both have built-in sway control. i have the Equal-i-zer and am very happy with it. you can get it from RVW for around $450 with free shipping.
i prefer mine over the Reese, since there's no drilling needed and no chains to fool with.
i added CIPA mirrors to my Avalanche which work great.
you won't need any air bags with a WDH.
your truck will easily do fine with the 21SS. my Avy has less towing capacity and i tow a heavier 23SS with no problems and no performance enhancements. it's 2WD with the same engine and same rear end.