Mine pfsense setup is very fast What I have is in System>Advanced>Miscellaneous>Cryptographic Hardware AES-NI and BSD Crypto Device is Chosen.  You must reboot after changes to this setting. Then in the openvpn configuration hardware crypto option I have BSD cryptodev engine selected.  There is no AES-NI option there because as long as AES-NI is enabled on the system openvpn uses it automatically.