The Argonauts were the best of each branch of something. Like the best archer, the best spotter, the best wrestler (Hercules), the best... whatever you can think up. They crewed a single ship to the east of the Black Sea to what is now Georgia. Many parts of the story actually fall into place, but it doesn't seem it be as 'true' as the Illiad.

The antstory about the Myrmidons is indeed from Age of Mythology, so we can't expect it to be very accurate. That is the problem with that game it mixes truth with fiction indescriminately. Who is to know what is what?

Quite likely the Myrmidons didn't exist. There is a possibility that there was a large effective band of mercenaries along with the troops that sacked Troy, but beyond that... Well nothing really.