General Questions

[Ludens]

Hearts indicate whether a unit has normal stamina or is hardy or very hardy. This determines the rate of fatigue. Letters indicate the reforms the units are tied to. For the Romans, the only relevant ones are Camillian, Polybian, Marian and Augustean. Regional units are independent of reforms (so you can recruit Brihentin and Neitos at the start of the game while the Gauls have to wait until the second reform). The number of dots indicates the level of barracks (MICs) required for recruiting them. Other signs are the tree (combat bonus in forests), the bush (can hide in high grass) and the skull with an I or C (scares infantry or cavalry respectively). BTW, missile weapons do not have a lethality stat: the number between brackets following their attack factor represents ammunition, not lethality.

Konny only included unit cards relevant for the Romans. If you want to get all available ones, you should download the old recruitment viewer available here.

It really sounds like you are playing at a battle difficulty other than medium. Sadly, higher battle difficulties do not make the A.I. more clever. They just give its troops a stat bonus, allowing their levies to beat up your heavies. This cannot be modded.