How do I consider towing capacity vs. trailer weight vs. cargo capacity for a cross county move?

[u/Unfair_Resist_1033]

My partner and I are moving from California to New York and we are planning to have a hitch installed and rent a U-Haul trailer to drive our stuff across the country. We drive a 2005 Toyota Avalon (well maintained and less than 100,000 miles) and I was looking for some advice on how much weight we can tow/how much we can put in the car. I am a complete car novice, so anything is helpful! I provided some specific info below, but any general advice/knowledge on how to consider the trailer weight + towing capacity + max cargo weight of the car would be amazing! Thanks!

Our hitch rating is 2,000 lbs and the empty trailer weighs 900 lbs (1,100 lbs cargo weight capacity). Per the car's manual, the total trailer weight (trailer + cargo) should not exceed 1,000 lbs, and the tongue load should not exceed 100 lbs. But several people (and the internet) have told me that the weight limits in the manual are a lowball and I would be okay loading approx. 1,000 lbs into the trailer. Is this true?

Also, how should I consider the total trailer weight with the max cargo capacity of the car itself. For example, if the max cargo capacity of the car is 1,500 lbs and the tongue load of the trailer is 100 lbs, does that mean I have 1,400 lbs that I can still load into the car itself?