Using paid plan and forwarding all responses

[brotskydotcom]

I am interested in using the paid plan to do "Send Email with Custom Domain" but I want all the responses to the sent emails forwarded to an address in another domain (in my case, Gmail). The instructions here say not to set up forwarding DNS TXT records if I have a paid plan. Is that because there's some sort of preferences UI on the paid plan that allows me to set up the forwarding in my account configuration? Or will I use DNS TXT records to set up the forwarding?