My '18 TRDP just turned 100k and I took it in for a full maintenance update. Let me know if I missed anything you would recommend be done as well

Oil Change
Filters
Power Steering
Coolant
Transmission
Differential
Brake
Spark Plugs
Grease Zerks
Evaluate all ball joints and bushings

*all the systems above are fluid flush/swap

You did more than 98% of vehicle owners will do to their vehicles at 100,000 miles. Main reason is, because of the list you listed, i suspect this was a $3500 ticket you had to cough up. Very few people do preventative maintenance, and on Toyotas they do less than anyone else because they are so reliable they just keep driving them. Friend of mine drove his 2003 4runner to like 330,000 before he had an issue that caused him to finally do some maintenance to it. Otherwise he drove the wheels off it, replaced tires and did oil changes and never touched it otherwise. Toyota is known for reliability and it shows, all the things you did honestly is great for peace of mind but truthfully not necessary.
Our plugs are known to get around 200,000 miles before they start going bad. Most drivers can get around 150,000 miles out of brakes if they dont drive like a woman in a hurry. Power steering fluid flush and change..... Meh i've never done that on any vehicle.... Our transmissions are "no maintenance transmissions" for a reason and you are not supposed to touch them. I drove my 1GR-FE tacoma to 275,000 miles before selling it and never touched the trans, diff, or power steering. Same with my now 230,000 mile 1GR-FE 4runner. I havent touched the trans, diff, or power steering fluids. You should be golden.... You changed things nobody does, i dont think you are going to hurt anything.

Maybe clean the MAF and throttle body if you haven't done so recently. Easy to do yourself especially the MAF, like 5 minutes. I found you tube videos on these.

This.

I assume you changed out TC as you listed diffs, but I also placed my front hub/wheel bearings. I planned to change out my CVs, but I pushed that out a bit as mine still look good.

Great information to know! Fortunately, my mechanic is a an awesome shop owner and the tab came to $1700 OTD. I felt that was pretty fair. I haven't had a car payment in two years and have never paid for more than an oil change, a set of tires and brake pads.

PCV maybe.

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I do trust what this guy recommends for the most part. He has several informative videos some bucking standard Toyota schedules.
The Car Care Nut - YouTube

Serpentine belt is cheap and easy

That sounds extremely fair. And you didnt even need to get under the car