What, you don't take drives out of a NAS once its installed unless you are upgrading them.

Depends on the use case

Zero or scramble it or don't send it.

If you had the drive encrypted to begin with, then it doesn't really matter.

Keep them unplugged and in a cool dry safe environment free from temp swings or shock damage, theft, etc.

And when in use, always make sure they are on conditioned power and kept cooll while operating.

You are going to need some CDN relays or something. 30k live viewers will destroy a single connection.

a wire or fiber

You should always zero a drive, if you can before sending back.

If a drive ever has sensitive data and you can't zero it, you shouldn't ever return it.

I used to go multiple times a week, then they took away PC games.
I used to go multiple times a month, then they severely reduced PC Part selection.
I used to go several times a year, now they remove physical media.
There's no reason to go to Best Buy, except maybe on Black Friday.

Check all the internal connections to make sure nothing got knocked out.