Hi, we went recently. Have ASD. Mad HP fan. Best holiday ever.
You definitely need to stay at a park resort for early entry to avoid too many people. There is background music everywhere but the HP music is the theme tune music so I found it fine (classical). Some places (Marvel area) it's too loud.
Download uber eats before you leave and you can get food delivery to the hotel. You can take food into the park. There are free lockers for small rucksacks whilst on rides you can't take bags on, free tap water everywhere. So we split the food etc between 2 small bags and it was fine.
The cheapest place to get universal park tickets was a site called Orlando attractions. I used the site Orlando informer for planning. The universal official app is essential for planning and checking live queuing times. It can be cheaper if less than 3 days to buy individual park tickets- have a look at cheapholidayexpert on Instagram as she went there recently and has some good budget tips. Also has videos of the endless summer rooms I think.
I used the single rider queues a lot (by myself) to avoid queuing for too long but there were small groups using them too. If you can't do coasters they will let you queue to experience eg walking through Hogwarts then exit before the ride. You can also use the single rider option for one person to test a ride to see if the others would like it. The Hogwarts and Gringotts ride are a mix of virtual and real. They are amazing. Lots of other things to do if no coasters eg ollivander wand experience, hogwarts train, celestina warbeck performances, etc.
There is so much HP stuff to see that I honestly think you could fill 3 or 4 days with that alone. We spent 7 days there, just in the park. It absolutely blew my mind. Also because of ASD we couldn't do a full day in the park so we needed rest breaks etc.
We tipped 20%, which is what my US friend said to tip. $1 per day per person to the housekeeping team.