Combat M2TW
From Totalwar.org
Various Combat Arms Usage
What I recommend is pick your faction and start a campaign. Go to the building browser for a settlement and right click on the troop producing buildings. They will list what troops you can get at what level. If you right click on the unit, it will pull up the unit card with a full description and the key stats. That way you can see your entire unit line up and what buildings you need to get them.
Beyond that, M2TW is not that dissimilar from other Total War games.
A list of Faction units and stats can be found by clicking on the 'M2TW Unit' link at the bottom of the page.
