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Amex Platinum is an easy card to get approved for. Since it's a charge card and not a credit card, it's less risk for Amex. You've shown good payment history since November, I honestly don't see them declining you unless something drastic has happened with your scores.
With Amex you're also likely not to get hardpulled, so you have nothing to lose there. I got my Platinum a few weeks ago, no HP.
Based on your scores and history, I don' think you'll be able to get CSP/R or the Ritz unless your income is very strong. Might be a better option to start with the Platinum now (which is a great card if you use all the benefits) and build up your scores. Once you're below 5/24 again, go for the Chase cards.
Edit: Ritz is not under 5/24 so you could try that one before you're under 5/24 again. But give your scores some time to grow. Chase is conservative, they don't like low scores with many new accounts. The Ritz is a Visa Infinite meaning it requires a 10k SL. If you can't qualify for 10k with Chase at the moment, you would just be wasting a HP.
If you have the Delta Gold, you already get half price fees for use of the Delta lounges. So while the Reserve does provide Delta lounge access, unless you are using those lounges a dozen times per year, from a Delta lounge calculation you are better off paying the half-price day fee.
Insert Important clarification: The Delta Reserve only gets you into Delta lounges. That applies to all the Delta AMEX cards.
The Delta Reserve also has the annual fee up front.
With the AMEX One Sign Up Bonus per card per lifetime, if you do decide to go for the Delta Platinum or Delta Reserve, best option is to app separately for each, before product changing your oldest to the one you want long term.
Mid-2013 Delta Gold, $2k
Mar 2014 Delta Platinum $10k, closed within 6 months because I misunderstood “lounge access” and “Platinum”.
Mid-2017, took a PC offer to move the Gold to Platinum for a small miles bonus.
Jan 2018 apped the Delta Reserve for the 40k miles plus 10k MQM.
Jan 2019 will close the Delta Reserve and PC the Delta Platinum ( 2013 open date ) to Delta Reserve and done with the PC and app movements.