Yes, and no. In theory, you could absolutely "back up" any physical media you have to prevent wear and tear to the disc, which is a completely legitimate use case. And it's not considered piracy because by buying that media, you purchased the legal rights to use it for personal viewing. However, if you ever gave a copy of that rip to another person (or gave that disc away to someone else without deleting your rips), you would be commiting piracy.

In fact, I believe that even viewing the media alongside another person is technically not allowed, although clearly that's not enforced unless you're doing some sort of public showing.

I use it for my own dvds/blu-rays, yeah. This is technically still considered piracy, but my personal view is that I'm fine paying for something once because the people who made it deserve to get paid, but I'm not fine paying for the same thing multiple times when the effort on their end to make the new version was basically zero. It would be one thing if there were physical costs like going from vhs to dvd, but that's not the case here.

I have a mix. Ripping your own is in line with format shifting. Putting a cad into a cassette for use in your car that didn’t have a cd player is the old school equivalent. I believe it is a valid fair use case.