I'd like to use a different email address for one-time passcodes (OTP), but I'd still like to receive other emails from Arvest to my original email. Is that an option?

Yes! In your profile, there are two tabs: Personal and Security. Changes made in the Personal tab, such as an email or phone number change, will affect how Arvest contacts you. Changes made in the Security tab will only affect how you receive the one-time passcode when logging in.