Donnybrook allows you to buy troops using force points, for each point you can buy 4 elite foot 8 drilled foot or 12 recruit foot. For the same point you have 3 elite mounted, 6 drilled mounted or 9 recruit mounted.
Each force has a free hero level character that commands the little army, and a special character for every unit choice you make, ( these are the same morale level as the units chosen.
A basic game of Donnybrook has 4 points of troops so a small force might consist of
Two detachments of 12 recruit musketeers.
One detachment of 8 drilled pikemen.
One detachment of 6 drilled mounted dragoons.
With the above force you get the free hero plus two drilled and two recruit level special characters.
The special characters have special abilities and these change depending on the faction you choose, factions range from the normal military faction through civilian mob, Covenanters,Cultists, highlanders, outlaws etc etc. (There's lots of factions).
The rules can be played with all the extra rules or none of them, it's up to you.
There's even a scenario in the book that allows you to fight with a warband rather than a skirmish force which means you fight with 1 figure units.
Lastly characters may be attached to units or not it's up to you and units are made up of between three to twelve figures, so if you buy two points worth or recruits ( 24 figures) you can organise them into any number of units between 3 and 12. So 4 units of 6 or 3 units of 8 or one unit of 12 and two units of 6 etc etc.
Clear as mud
, but I hope it gives some idea of the size of games.