2/3 is the most common.

Yes, if you have 3/3 keys you don't need the coordinator file, but I wouldn't want to be in that scenario obvz.

Xpub/coordinator file is sensitive information but not critical.

If someone gets a hold of this file they can see your entire transaction history.

Encrypted cloud backup is a good way to store it digitally, but that shouldn't be a substitute for storing it in many places physically.