I had to update macOS Monterey during installation, which took about 30 minutes with the computer turning off and on two or three times. There
is an option to defer the update until after installation. Looking at posts in other threads, it appears that some people didn't need to update.
Like
@Avenger (post #2), I discovered that File Vault was turned on as part of the install. I didn't see File Vault as an option during installation, although maybe I missed it. I've since turned it off.
I had no other "issues", including with Time Machine (see post #3), for which I created a new APFS volume on an existing disk. However, it was my first Time Machine backup that alerted me to the fact that File Vault was on. I got a pop-up warning that my Time Machine volume is not encrypted.