Well until this point nobody has ever prooven any AI improvements in Alex over the other Exe, but retraining is a nice feature.
I personally think/experienced that the Alex AI is very passive and sloppy protecting their settlements from other factions, but again this is my experienced. It might not have anything to do with the Exe.

Diplomacy I would say is just a matter of your playing and luck. I played long rome.exe sessions were I had large armies at the boarder of my empire and I never atacked any other player and in Return I had a long time peace with the other factions.
On Alex I had a fullstack of carthagenian troops guarding a bridge and the ptollis atacked me with just 2 phalangitai...
I guess it just might be random sometimes, because the AI just picks a target city and than tries everything to get it.