I think you are mostly right. If you book the KLM flights shown with the KLM light fare (VLX76OBA) on the KLM website:
- As a PM you can immediately reserve economy comfort seats on the website or app after booking (not during the booking process where you would be charged), and as a GM you can either pay or get free access to economy comfort 3 days before the flight.
- The trips will NOT automatically show up in your Delta accounts, as there are no Delta flights. I don't know if you can add them to your Delta account, but you need to do everything on KLM website anyway.
- You will receive 1 free checked baggage as a PM or GM. It will show in the booking or app AFTER the booking is completed.
- You will earn skymiles and MQD'S based on KLM V booking class.
- I think you should NOT get access to the sky club in LAX, as with AMEX Platinum it does state it must be either a Delta operated or Delta marketed flight. However I was able to access the Sky Club in Atlanta at the end of last year using my AMEX Platinum while flying an Air France marketed and operated flight. You would have access to the KLM lounge in Amsterdam during your connection, as a PM or GM.
I am based in Europe and fly a lot on AF and KLM light fares.