Questions about time machine

Yes, to all of that.

https://support.apple.com/guide/mac-help/what-is-power-nap-mh40773/mac

If it doesn’t get a chance to back up in a long time, it will create another full backup. I don’t think it is a prescribed time. Just when it determines it cannot work from the current set. Time Machine references the FSEvents database which is a log of every file system change. I imagine that database gets stale or the history is limited to a certain size or length. When there is a gap between the last backup and the events, it has to create a new, full backup.

1. Almost everything unless you exclude it.
2. No, but you should let it work at least once a week. I think it must be connected to the power adapter in order to backup.
3. The first full backup is essentially a duplicate of your drive, so it takes a while. The incremental backups are dependent on how much data changed. I couldn’t give you a specific time because I rarely notice it is running.
4. You Migrate them either in the Setup Assistant when you first start the Mac, or later via Migration Assistant. For MA, don’t create the user prior to migrating. It will create the old account when it migrates.
5. You find and delete the in the Time Machine interface. But, if you want to manage your backups, use something else. Time Machine is designed to turn it on and forget it, not for micromanagement by the user.
6. No.

How quick is time machine backup?

Much will depend on your infrastructure.

My TM backup route: 2019 MacBook Pro (macOS 11.1) - ethernet - router - NAS

My initial TM backup takes about 45 minutes for 85GB data and system.

Incremental daily backup takes about 10 minutes for 25GB of new and changed files.

If I was backing up to a drive attached directly to the MacBook, backups would be faster.

There's lots of chatter about making TM backups but not so much about restoring TM backups. Before proceeding you should thoroughly research the TM restore process. In my case, using Internet Recovery, a TM restore from NAS takes 45-50 minutes to the login screen.

 When your initial TM backup is completed, you should check that it will restore but be aware the restore process initially completely erases the destination (internal) drive. This is a typical "Catch 22" situation because although rare, if your test restore fails after the destination drive is erased, everything is lost. That's why it's wise to hold a current backup of all your personal files on a separate drive. Alternatively you could explore a third party cloning software such as Carbon Copy Cloner or SuperDuper which can produce a bootable clone of your entire system, applications, personal settings and data. I use CCC as a complement to TM; it's very fast and accurate. CCC offers a fully functional 30 day trial which you could use to produce a bootable clone as insurance until you were sure your TM backups could be successfully restored. Don't store the bootable clone on the same drive as your TM backups.

That’s fine. It’s like two to three weeks when I’ve seen it kind of give up on you.