By changing key of your hardware wallet, do you mean the PIN? If so, then no, it won't impact the hidden wallets. The PIN is used to grant access to the seed, but does not modify the seed itself, while the encryption passphrase actually modifies (encrypts) the wallet seed.

Yes, you can recover your hidden wallets using the recovery seed. Simply load the recovery seed into a new device, and set up passphrase encryption. Your old wallets will be accessible by simply re-entering your old encryption passphrases.