Great points above. While it looks like the Citi Rewards +, Double Cash, and Custom Cash could be a powerful cashback tri-fecta, they aren't the absolute best-earning cash back cards. And the other risk is that TY points could be devalued easily and quickly by Citi.
Meanwhile, there are other options, some easier and even better.
AOD FCU Visa Signature gets a flat 3% cash back, uncapped and uncategorized with no bothersome transfer of points of risk of devaluation.
https://www.aodfcu.com/visa-signature-credit-card/
US Alliance FCU Visa Signature card is getting a flat 3% cash back also. (However, they previously made the 3% return a "temporary promotion" so they don't seem as committed to long-term 3% cash back.)
https://go.usalliance.org/signature-card-rewards
US Bank Altitude Reserve earns 3% cash back on all mobile wallet purchases and 3% back on all travel purchases. It does have a $400 AF but it has $325 in travel credits to offset it, among other benefits.
https://www.usbank.com/credit-cards/altitude-reserve-visa-infinite-credit-card.html
Bank of America Premium Rewards (with Preferred Rewards Platinum Honors status) earns 2.625%* uncapped and uncategorized plus 3.5% on all dining and travel, also uncapped and uncategorized. The $95 AF is completely offset by a $100 airline fee credit and TSA Global Entry reimbursement ($100/4 years.)
*One feature of Platinum Honors status is a 75% boost in base earnings rate of credit card rewards. 1.5% x 1.75% = 2.625%
https://www.bankofamerica.com/credit-cards/products/premium-rewards-credit-card/
https://www.bankofamerica.com/preferred-rewards/
USAA Limitless Cash Back (no longer available but could be reintroduced in the future) offered an uncapped and uncategorized 2.5% cash back with no AF. Cardholders were grandfathered into the program after applications were closed. Some of our My Fico members still have the card.
Alliant Credit Union Visa Signature earns 2.5% cash back on all purchases. However, it has to overcome a $99 AF after the first year. The breakeven point with a 2% card comes at $19,800 annual spending (or $1650 per month.) The return on $2K monthly spend or $24K per year is 2.0875%. The return on $3K monthly spend or $36K per year is 2.225%. So high spending on the Alliant CU Visa would exceed the earnings on the Citi combo. The additional benefit is that it could be a simple one-card daily driver with a return that exceeds 2% instead of having multiple cards.
https://www.alliantcreditunion.org/bank/visa-signature-card
Chase Freedom Unlimited earns 1.5% but cash back can be redeemed (for travel through Chase portal only, not cash back) for 50% more value if combined with a Chase Sapphire Reserve. That works out to 2.25% in travel value, uncapped and uncategorized. While CSR has a $550 AF, there are many credits and benefits to help offset it. Similar to the Citi Combo with the Custom Cash, a Chase Freedom Flex could be added for 5% (augmented to 7.5%) on quarterly categories.
https://creditcards.chase.com/cash-back-credit-cards/freedom/unlimited
https://creditcards.chase.com/rewards-credit-cards/sapphire/reserve
https://creditcards.chase.com/cash-back-credit-cards/freedom/flex
Fidelity Rewards Visa (Elan Financial Services) is a 2% card can earn 2.25%, 2.50%, or 3% cash back if a cardholder is a member of Fidelity's "Rewards Plus" program with assets under management of $2M+. Link offers a $100 SUB which isn't available everywhere.
https://www.fidelity.com/go/visa-signature-rewards-1001?offer=FCBA
https://www.fidelity.com/rewards/overview
While it's a little bit of a stretch for the "Cash Back" category and mixes personal with business cards, the Charles Schwab version of the American Express Platinum card allows you to redeem MR (Member Rewards) points FOR CASH at 1.25 ccp instead of the base 0.6 cpp with the traditional Platinum card. And the American Express Blue Business Plus (no AF) earns 2 MR points on up to $50K annually (average $4,166 monthly.) Using the BBP as an uncategorized card and transferring points to the CS-AXP would allows redemption at 2.5% return on up to $50K annually. The drawback is the high $550 AF on CS-AXP. However, for the right profile, this is still a viable option. The CS-AXP has a $100 AF credit for members with $250K in holdings and a $200 credit for members with $1M+ in holdings. This is in addition to the other normal AX-P card credits including $200 annually for UBER/UBER Eats, $100 TSA Global Entry credit (every 4.5 years), $100 in Saks Fifth Avenue annual credits, and $100 in annual credits for resort charges within The Hotel Collection. If the Platinum card fits your spend and lifestyle, it would be completely reasonable strategy to use it for a catch-all cash back strategy*.
*However, the normal "best" redemption of MR points would be for transfer to travel partners through AMEX where the 2.5% valuation could likely be exceeded.
https://www.schwab.com/credit-cards/platinum-card
