This is the Chase Marriott thread
Chase Marriott Bonvoy Cards, 2019 to present
Perhaps this thread should be merged into it, but since you asked about Amex:
If you get the Amex Business, the 15 ENC stacks on top of the 15 ENC from the Boundless (or any other personal card). To maximize the ENC per year you would get an Amex Brilliant (25 ENC) plus an Amex Business (15 ENC) for a total of 40 ENC.
Check this chart for eligibility:
https://frequentmiler.com/marriott-card-eligible/