You'll have to have a brokerage account with Schwab before you can apply for any AmEx products. It'll be a HP to join Schwab plus ChexSystems.
Consideration for either Platinum or Investor CC is based on AmEx UW rules. So, yes these cards are "true" AmEx versions, and if you're top heavy on current revolvers, then you might as well pass. The SUB rules/restrictions also apply.
The AF is not waived on the Platinum.
ETA - the Schwab Investor CC is not "metal"
Funny about the checksystems, it seems only if you want the BANK checking account and debit card....which they denied me for due to a low checksystems score (a whole other story) BUT I was able to get a debit card attached to my brokerage account with no issues, only difference is the BANK debit works in Europe atms and the BROKERAGE debit does not......I have both cards and no issues with applying or with the service they are both true amex cards and the platinum has all the same perks and customer service, the very cool part is the platinum now has a "invest with rewards" button to move my MR points to cash to my schwab account where I can invest or take out as cash from the debit card. Many mention the conversion rate to cash is much lower than travel rewards, true BUT it certainly is another option.
I am not sure of your availability with amex for another revolver, I was recently told only 5 revolvers and to get approved for my last one I had to close one....if you can get six please let us know....and that included business and personal revolvers....Good luck if you proceed forward!!