Most of these topics are covered in separate threads:
1. Purchases of merchant gift cards typically earn points and count toward bonuses. Purchases of Amex, Discover, MasterCard, VISA cards are more problematic. The key thing to understand is that American Express audits accounts, and transactions that are not flagged by the automated system may still be disallowed later.
2. Airline tickets purchased with miles are not covered by the Travel Delay, Interruption or Cancelation benefits. Tickets purchased with Membership Rewards points are covered. Partial payment with airline credit does not invalidate Travel Delay, Interruption or Cancellation benefits, but it does invalidate lost baggage benefit.
3. The Round Trip requirement applies to the full itinerary. Individual tickets can be one-way.
4. The Uber benefit applies only to the primary card. The card can be linked to any Uber account.
6. American Express does not use the term "Authorized User" in the same way as bankcard issuers. Additional Platinum cardholders receive nearly all of the benefits provided to the Basic cardholder, but in cases where the benefit has a capped monetary value the cap usually applies per account, not per card. You can also add free Gold or Green cards to a Platinum account. These cards earn rewards for spending at the same rate as the Platinum card (not at the rate of separate Gold or Green accounts).
7. Every American Express card has its own number. Additional cardholder can create separate online accounts, but this is not required. The Basic cardmember can see all activity on all cards. Membership Rewards points from all cards are credited to the Basic cardmember. Initially, transfers can only be made to airline or hotel accounts in the Basic member's name. After the Additional cards have been open for awhile (90 days?) transfers can also be made to their airline and hotel accounts. Membership Rewards points cannot be transferred to any other Membership Rewards account, nor to anyone else's airline or hotel accounts.
Appreciate the answers....all makes sense.
I re-read the terms for trip cancelation/inturruption/delay, and it seems like I misread previously, and doesn't outwardly say that using ff miles in combo with the card counts - which is odd since it does allow you to use frequent flyer 'or similar' vouchers, coupons, etc. in combo with the card. but is what it is.