I think the seat belt warning is a legal requirement - it should be reconnected before MOT.
The sloppy driving warning (AKA lane departure) is quite useful, it will make you a better driver. It does not go off without due cause; when it sounds you are wandering all over the place, or forgot to tap your indicator before changing lanes. When I first got the car it produced regular beeping sessions - nowadays hardly ever. And no, I don't press it off on startup. But I do press it off on secondary roads where they have been messing with the white lines.
The FCM warning set to far has saved the front end of my car twice, despite the occasional false alarm.
The road bend bong can be switched off in the navi menu.
The boot IS beepless on manual.
The ACC "radar lost" beep can be annoying, but it does warn about an unexpected acceleration surge.
And the "brake" beep on ACC one second after a full stop warns you not to hit the bloke in front.