With a mixed army I generally do something like this against most armies, which generally are mainly infantry:
Assign Sturgian skirmishers as Infantry in Party screen.
Decide if you want to Hold Fire.
1. Place Archers in front of Infantry. Spread out (F3-F3). Face Direction, so they don't spin around if skirmish cav circles them. Preferably Archers are on higher ground and with good field of fire. A treeline is also a good place.
2. Infantry - Shield Wall or Square (vs Cav). They are close behind or on the left of Archers (to soak up cavalry attack).
3. Horse Archers - Loose or Scatter Formation - (Fire at will) Charge (unless there is a river or other obstacle they can get bogged down in.)
4. Cavalry - follow me. Lead them to your right flank and move forward.
Let the enemy come to you. If you are outnumbered, they will.
(Archers+Infantry - Fire at will)
Ideally, your HA will draw away flanking enemy cavalry.
When main enemy force (infantry followed by archers) are closing with your Archer line and throwing stuff at them:
1. Infantry - Charge!
2. Cavalry - Charge!
Ideally you want the enemy infantry taking fire from left flank from your HA (who has circled around them), and from the front by your archers and skirmish infantry. At the same time.
You also want your cavalry to charge the following archers, which they will, if those are closest to them. Or you can hold the Charge order and just have them follow you through the archers.
The bulk of the enemy force (not Khuzait or other cav-heavy force) will now take massive casualties in a very short time and will be boxed in. Ideally, the infantry will break and rout. Your infantry will be almost in melee range of remaining archers.
You have several options, depending on the circumstances, reinforcements and terrain etc. Archers can be given either Advance (F1+F4) which makes them fall back if enemy is too close or Charge if you want more arrows in fleeing enemy bodies.
Now really everything depends on your battlesize settings etc. You may need to pull all troops back, regroup and do it all over again. Or not.
Anyway, that is the general idea from which I order around a mixed army.
Edited to add: No mods. Realistic settings plus highest AI setting, except damage to player 2/3. Depending on difficulty of battle I often don't have time to engage too many enemies myself. The timing of the Charge commands (inf and cav) feels crucial.