Depending what precisely you mean by the second one, you may not even need an AM/support for that.
They won't help me use the platform, but they will still address issues with the platform. If you run into bugs, things not behaving how they're documented, or something that simply isn't exposed/available to customers they seem to be pretty good about getting it resolved regardless of your spend or support level.
(On my personal account with minimal spend, no AM, and no support... I've had engineers from the relevant teams email me directly after submitting a ticket for issues.)
So yeah, "if you know what you're doing" you probably don't even need the paid-for support.
Hard disagree. I have to engage with AWS support almost once every 6 months. A lot of them end up being bugs identified in their services. Premium support is extremely valuable when your production services are down and you need to get them back up asap.