Unless you are wealthy being NEET is generally not a good thing IMO because you will feel crappy about being low status, and you will lack resources. Not sure what your definition of doing nothing is, but reasonable ones include eating at nice restaurants, expensive video games, gym memberships, courting mates, concerts, clothes, etc... doing nothing costs a fortune.

Needs expanding. Based on my personal experience with long vacations ... Yes, provided you work at home.

Just sitting on your ass all day playing games is pretty close to sticking a wire up your head. That's a lonely existence. It can be fun, if you turn your self-reflection off and just let yourself go. If you have enough cash, you can buy and watch what you want. But that's bound to be unhealthy, so I guess you'll end up with health problems at some point.

"Not in Employment, Education or Training" is not a bad thing. Retired people are NEET, kind of. And they can do just fine. So imagine what retired people would do. Maybe go on a world trip. Maybe have quiet rest? I think it's a great idea to position yourself as such that you don't need to work to live (UBI woooo), but to then go and just sit on your ass all day and just consume is boring.

Don't be a shut-in your whole life. Don't be a workaholic your whole life. Experience more.

Depends on which individual.