I’ve towed an 1800 lb pop up with a 2006 and a 2016 Sienna. I used air bags on both and highly recommend it. I’ve got a crazy bike rack that increases my tongue weight to about 400 lb.
But, I’m pretty confident that with just the pop up and cargo you will experience sag. They are less than $100, install in an hour or two and haven’t let me down yet. For what it is worth, I’ve installed mine separately, running the lines to the rocker panel just forward of the rear wheel well and just pump them up with a bicycle floor pump.