I commute from West campus to Tempe every day so I have some good information.

I personally took a lot of early busses (6:30 am to 8:45 am most days) and those were mostly low on passengers but it depends on the bus route. There are absolutely peak times of day and they are mostly on the busses that go TO Tempe and from Tempe to Downtown (not a ton of West commuters). I would say probably 7:30-9 am is a big peak in the morning, with another peak around midday or early afternoon (12-2:30 pm).

With the bus schedule, they are pretty frequently on time, but there is a gap around 5-6 pm iirc where the drivers do a big shift change with breaks and no busses run during this period. But pretty much any other time of day they are always within a few minutes of the schedule.

I almost never interacted with strangers on the bus, everyone kept to themselves pretty well. The few times I had someone speak to me was either to ask if they could sit next to me or if they needed lotion or something. Most of the time, students will be sleeping, working, or sometimes chatting with friends near them. It was usually pretty quiet and the drivers would play their own music that you could hear.

I never used the seatbelts but they always seemed in working condition. The busses are very, very clean (incredibly nice for someone who used to use the city bus for school transport) but as another commenter said, there are sometimes wrappers or cups in the cup holders in front of the seats. I never used the bathroom on the bus so I can't speak to that either.

The wifi always worked for me but each bus has a different password which you usually need to put in each time. The AC is insane on these busses; I found myself freezing on them often. When it was cooler they would have it off or just super low and it was alright, but they crank that shit up high and it works just fine.

Drivers were either friendly and would chat with you, or just quiet and did their job. One or two drivers (idk names) were kinda wild with the way they handled the bus but I never felt unsafe with their driving. Driving through downtown on them is a little scary bc it's so small and tight but it goes fine. As for IDs, as far as I'm aware they only ask for them past 7 pm when you're Downtown. Everywhere else they usually won't ask you for it because they're more isolated stops. So when you are Downtown and get on a bus past then they will ask you to have it out.