Do I need Yubikey authenticator app?

I am confused about the the YubiKey authenticator app for Bitwarden.
I have a premium account and enabled YubiKey when account is logged out.
I am not sure what if any benefit the authenticator app would bring
thanks in advance

There are two ways to add a Yubikey in Bitwarden. 1. Under the Yubikey OTP section which provides a one time password that autofills when you tap your key. 2. The second method is to add the Yubikey under the WebAuthn section and then tap your key. This works for nearly all Bitwarden apps but not the desktop all, at least on Mac. This is considered a more secure method.

Neither require an authenticator app to work. Just the key.

As a best practice you should always have a minimum of two keys registered so you have a backup stored safety away. You also should print your 2FA recovery code and store it safely in case you ever lose your 2FA method and need to temporarily disable it.

Also, don’t forgot to keep your master password printed and stored safely and an exported version of your vault on a usb key.

The Yubi Authenticator app is for TOTP codes. So there are 3 ways to use a Yubikey with BW, the 2 ways described above by 222 plus the Yubi Authenticator app.
If you’re not using TOTP via the Yubikey then you don’t need the Yubi Authenticator app.