About validation: Because of the type of questions (salary???, Bankaccount number ???) we have chosen for a personal visit by a rep. This visit lasted 2 minutes. No problem.

About insurance: I have called the Netherlands FB-AMEX and they say that there is no requirement to fly a specific airline for insurance purposes. However, if due to COVID you are unable to return, AMEX cancels the insurance after 120d of travel. Unless you make a special arrangement.