Three things: is it on track, what needs a decision from me, and what has gone wrong. Everything else is padding that makes those three harder to find.
A report that leads with activity is answering a question the client did not ask, and it trains them to skim.
A list of completed tasks says you were busy. A note saying phase two slipped four days because a dependency was late, and here is the effect on the date, says you are managing.
The second is shorter and considerably more reassuring, because it demonstrates you would have noticed.
Weekly for active delivery, monthly for retainers. Consistency matters more than frequency.
Yes, early. A problem you reported is competence; one they discover is a surprise.
The assembly, yes. The commentary is the part with the value.
Half an hour with your own data usually saves reading three of these. The guides will still be here afterwards.