The only "checkbox" in Turbotax is a privacy function that allows Turbotax to "view" your refund information for purposes of marketing the refund transfer service to you. (Even though you are using the software to prepare your return, the company does not officially know what your refund is and can't market to you unless you check that box.). That checkbox has no other authority with the IRS.
Form 2848 is a special type of "power of attorney" that allows you to designate someone else to discuss your tax returns with the IRS. It does not give the person any rights under a power of attorney for any other situations. I would sign several copies, mail one to the IRS (certified return receipt), and give your friend some copies. There's probably no chance of getting the advance $1400 payment now, but you can claim a rebate on your 2021 tax return if you don't get the advance payment.
For identity theft, if you know you are the victim of identity theft, you can file a form 14039-T affidavit.
You can also opt-in to the IP-PIN program. The IP-PIN is a 6 digit identity theft PIN that you must use when e-filing (in addition to the lower security 5 digit "e-file PIN" or AGI) and you must include on any written submissions. The IP PIN changes every year, the IRS will mail a new one in December. Once assigned an IP PIN, you must use it every year and you can't opt out.
https://www.irs.gov/identity-theft-fraud-scams/get-an-identity-protection-pin
If you don't have an IRS online account, you should make one. It allows you to view certain tax information, and more importantly, getting your account blocks anyone else from fraudulently setting up an account in your name.
https://www.irs.gov/payments/view-your-tax-account
If you think you might be a victim of identity theft, there are several steps you can take.
1. Make sure all your online passwords are secure and different from each other. You might want to use a password manager,
https://www.pcmag.com/picks/the-best-password-managers
2. Go to www.annualcreditreport.com and get your 3 official free credit reports, and look for unauthorized accounts.
3. You may want to lock or freeze your credit bureau reports. A credit "Freeze" is something required by the federal government and has certain rules, a freeze is the same at every credit bureau. A "lock" is a program offered by the credit bureau on its own terms, each credit bureau may have different terms and conditions for their "locks" and they can charge for the service or may try to upsell you on other services.
https://www.nerdwallet.com/article/finance/credit-lock-and-credit-freeze
Here are some other resources for identity theft.
https://turbotax.intuit.com/tax-tips/security/identity-theft-what-to-do-if-someone-has-already-filed...
https://turbotax.intuit.com/tax-tips/security/identity-theft-7-steps-to-reclaiming-your-identity-and...
https://turbotax.intuit.com/tax-tips/security/tax-tips-if-you-have-had-your-identity-stolen/L5t5bXQs...
https://turbotax.intuit.com/tax-tips/security/guide-to-irs-form-14039-identity-theft-affidavit/L7YTP...
