The three Hellenic Seaways Aeros are identical.All the seats are the same, "airplane" type, there is a 8 seats central aisle and side aisles near windows with 2 seats each.
I couldn't tell you what the AK zones correspond to (these 3 ferries have just been acquired by Hellenic Seaways last year)
There is no AK zone more comfortable than another.
If you are worried about the comfort of the trip, why don't you choose a traditional ferry with Anes Lines or Saronic Ferries which are much more comfortable?
You will have a real ferry travel experience,
Tickets are about 2 times cheaper, the journey takes only 30 minutes longer, and they are less sensitive to rough seas.
“Also is there a way to seat select in advance or do you just grab the
seats as you board?”
In a highspeed catamaran like the Aero you are stuck in an assigned seat like in an airplane for the entire duration of the journey.
With a traditional ferry you can sit wherever you want, there are seats with tables where you can be face to face, you can go to the outside decks and enjoy the scenery.
In the port of Piraeus all departures to Aegina are from Gate E8 which is located approximately 1/4 miles from the metro exit (5 minutes walk)
If ferryhopper is convenient for checking schedules and prices, buy your tickets directly on the ferry company's website. If you have an electronic ticket you can board the ferry directly, but the majority of travelers take their ticket at the sales offices at the port, there are located on the quay just in front of gate E8.
Plan to be approximately 45 minutes or more before departure time.