For my taste, to get the most realistic and best AI behavior
- AI Ranking to Colonel (1)
- Use All Behaviors X
- Activation Bonus -X-- (2)
- AI Detect Bonus --X-- (3)
- Aggressivness -X- (4)
- Give AI More Time X
(1) At lower settings Athena will not user her leaders very sensibly. Good generals will not be put in charge of the best armies and stacks and will sometimes be sent out on scouting missions (5), which is a total waist for a good commander. The lower the setting the worse she is.
(2) As far as I can tell, this increases all the AI's generals' strategic rating by 1. I've seen this during battles, that generals that I know are 3-1-1 are 4-1-1, etc. Having an AI opponent constantly be more mobile will wear you to rags trying to follow him everywhere and is not very realistic IMHO.
(3) I've not played around with these settings, but an AI opponent that "sees" much more than it should will not "play" normally and you will learn to play far differently than vs a real player who doesn't have such a viewing advantage.
(4) This is only relevant to patch level 1.16 and most of the 1.16RC (Release Candidates). I've not player around with this setting, but before 1.16 setting to medium would have Athena performing some pretty outlandish deep raids, which usually ended is the raiders being cutoff deep in enemy territory with no supply. So with 1.15 and earlier, set to Low Aggression. At 1.16 set to medium. Athena still doesn't know when to call it quits when she's being besieged and hounded in and around Pittsburgh and return to the bosom of the south, but she will keep you busy trying to nail her down.
(5) Athena does something that you will probably not see allowed in any PBEM game. She sends generals into your territory on Green/Green (Passive Posture/Retreat if engaged) with the Evade Combat button pressed to scout out your side of the front. I've often seen her send a few into very deep enemy territory to gather information.
You will not often see these scouts and sometimes get a message while moving over one such undetected leader stating that your moving unit avoided combat in a region where you see nothing there and have 100% MC. You cannot attack these leaders successfully and they will never starve for lack of supplies. You can drive them off at times with cavalry, but they will just sidle off to a neighboring region and return later.
They generally stay stationary in their regions as long as the front has not shifted, so if you've detected one it's good to know that it's there and just a leader lest you drive yourself crazy chasing ghosts.