I am aware that the introduction of BIP-38 resulted in a standard for passphrase-based encrypted private keys utilizing AES. What is not clear to me is whether these can be generated from HD wallets? Are the HD wallet seed-based private keys, then, considered encrypted private keys? Or do they follow the general private key format, since they are derived through their own HD wallets' processes?
The private keys themselves can be generated with BIP 32 and then those private keys encrypted. Private keys generated with BIP 32 are not special private keys; they are just normal private keys and you can do exactly the same things to those private keys as you would to any other private key.