I tow my ATV trailer with 2 vehicles loaded behind my 5th. It works well - no sway or excessive bouncing, but the total weight of trailer and vehicles is less than 2500 lbs so my tongue weight is pretty low. I don't go over 65 even when I could just to give me some extra margin if I need to stop quickly.
The only issue I have had is turning sharp - the tongue of the ATV trailer is not long enough to avoid the front of the ATV trailer hitting the back of the 5th wheel when turning too sharp, and I have bent the ATV trailer angle iron and cut grooves in the back edges of the 5th on each side.
Of course, backing more than a few feet is not productive so you have to make sure you can drive through or give yourself enough room to unhook the small trailer if necessary.
Having the ability to take extra stuff (ATVs, boats, etc) without spending large bucks for a toy hauler is well worth the cost to get the hitch installed and the extra hassle of turning and backing up. I will do it if I ever change 5th wheels in the future.