Ignoring militia, each faction has two troop trees: a branching regular one that only goes up to tier 5 and a single track noble tree that goes up to tier 6. So, for Vlandia its noble troop tree starts with a tier 2 squire and ends with a tier 6 Banner Knight. AFAIK noble horses are just for Lords/Ladies, cavalry need mounts up to tier 3 and war horses above that.