I have a technical question.
A wallet is protected by a password, which encrypts the key.
Is it possible to "merge" two encrypted wallets into one and have a completely new database, if they are encrypted with the same password?
Is there any paper on how the encryption works?
No you cannot, as there is no wallet that can have multiple passwords for different private keys.
All wallets even those with imported keys share the same password, therefor render it impossible to "merge" two different wallets with different passwords into one.
If you need info on password encryption for bitcoin core you could always dive in here; (google AES-256-CBC and SHA-512)
https://en.bitcoin.it/wiki/Wallet_encryption/KX