openssl_get_cipher_methods -- get per-cipher keylengths?

I'm deploying a php app that makes use of "openssl_get_cipher_methods" Its config defaults to $config['cipher_method'] = 'DES-EDE3-CBC'; and $config['des_key'] = '123456789012345678901234'; where "This key (generically named, 'des_key') is used to encrypt the users imap password which is stored in the session record. For the default cipher method it must be exactly 24 characters long." The project recommends $config['cipher_method'] = 'AES-256-CBC'; as a 'better option'. IIUC, as it uses "openssl_get_cipher_methods", additional ciphers _are_ supported; as listed by https://www.php.net/manual/en/function.openssl-get-cipher-methods.php That list includes [23] => aes-256-cbc [32] => aes-256-gcm [93] => chacha20-poly1305 What, if any, are current recommendations -- either specifically for php, or in the general case -- for cipher usage of 'aes-256-cbc' vs 'aes-256-gcm' ? How are required php-config keylengths, in characters, determined for any available/usable cipher? e.g., for 'chacha20-poly1305' ?