Your more limiting factor on the 4Runner will be the payload capacity. Look on the driver door jamb for the yellow tire loading sticker to get your payload capacity. Take that number and subtract the weight of passengers and cargo. Whatever amount is left over will the weight that your tongue weight and hitch assembly cannot exceed. Using that number will also give you the max travel trailer weight you can tow.
For example friend of mine has a 2015 4Runner Trail. His yellow sticker shows 825lbs. Minus him, wife, dog gear and he has about 400lbs left over for tongue weight.