That payload number is including passengers. Toyota has no idea how much your passengers will weigh or whether you will even have passengers. If you weigh over 150lbs, it also includes that amount too.
Also, your intended 1550lb popup is EMPTY. No water, no food, no clothing, no fishing equipment, no chairs, no firewood.
Depending on how many passengers you have and what you plan on doing while camping, your realistic load will be somewhere between 2000 and 2500lbs. The first rule of RVing is, it always weighs more than you think it does.
Now, is that the end of the world? For some, yes. For others, no, they just start adding suspension helpers to their trucks, upgrade their tires, and hit the road.
Some people will tell you to sell your truck and get a 1 ton, period. The other camp will tell you that such people are "weight police" and "worry warts" and that your Tundra will haul a camper just fine.
All I wish to do here is provide you with a clear picture of what you are getting yourself into if you choose to move forward. You need to make your own decision and take responsibility for it.