When you put together the antagonist groups of NPCs/monsters for a fight, how do you match them to the strength of…

When you put together the antagonist groups of NPCs/monsters for a fight, how do you match them to the strength of…

When you put together the antagonist groups of NPCs/monsters for a fight, how do you match them to the strength of the players? Combat seem either to easy or to hard in my group.

In the DW-rulebook they are either very weak with 3 HP, probably “cannon fodder”, medium or the strongest monsters have as much HP as the PCs, although they have better armor and some imunities, including fictional positioning. How do you do it?