If your "hold wallet" is cold storage, for instance a paper wallet, a single address is indeed easy. But it's better for privacy to use a new address each time, and it's less risky to use a different paper wallet each time you add funds. That way you don't expose all your funds when you want to send a small part of it later on.
but isn;t a single address how these hardware wallets work? im way more nervous about having 50 different address and key pairs and losing 1 or more than keeping up with and securing a single address and key pair.
Most (if not all) hardware wallets use more than one address. You don't need to backup each individual private key, they're all derived from the same (24) mnemonic seed words.
But that has nothing to do with Bitcoin Core.
so i can test the wallet backup in btc core without having to have a second computer running core?
It depends: it doesn't hurt to be overly thorough and start
from scratch to see if you can restore everything from just the backup you made on a USB stick. I've actually done that years ago, but I don't do it anymore.
Note that a few more backups is better, just in case the USB stick breaks (after a while). I prefer to use different brands.