Ine

Most airlines to the US want you to check in 3 hours prior, although often 2 hours will do. However if you are flying on a weekend expect a lot of passengers and not only that at the moment Schiphol airport is often a mess. Expect long lines, not only to check in but also security are having problems since they seem to be understaffed. In case you are flying business class you will see shorter lines.

As far as I know no testing at the terminal in Amsterdam anymore. So you have to arrange it yourself before embarking. It can be done within 72 hours prior. Never heard about the captain making statements about how many Covid patients either by passengers or crew.

No you do it on the platform where the train departs or arrives. On some stations it is before you can enter the platform to open the gate.

It depends on your neighbours! To us never again.