To be honest, i’m afraid i am not sure there is an general statement i can make. It depends. (Ok, i can actually be more helpful. :-) ) Thinks i consider when placing troops on the field:
- unit type
- number of units in that group
- obstacles to movement
- Types and likely trajectories
- what group would attack which one
I have constructed 3 scenarios where i would choose different groupings
In a head to head battle where the enemy also has ranged units and trash units but his ranged units are stronger, i would place my halbadiers in two groups and place swordman and albalests behind the lines.
When there is an obstactle the abalests can hide behind and one enemy flank is stronger i would place it as the middle picture.
If in the bottom right there is a group of enemy wolf riders i would place a mix of speer and sword units so that the wolf group will run into them and have the abalest use my melee units as an obstactle.