Usually a melee weapon, an oh-crap mid-range weapon (any swap-and-click-to-stagger option) and a bow for mostly sneak shots. So, three.
My basic toolbar is pretty completely standard by now:
Bow, Melee, Stone Axe, Midranger, Free*, Frames, Water, Bandage, Free*, Free*
* not empty ofc, usually tools, or turrets, or additional weapons.
For hordes, bow gets ditched if I have a replacement, stone axe swapped for a proper repair tool, free slots filled mostly with whatever boomers I can find and then some more weapons. Maybe one slot for a tool I predict needing fast (knife for corpse removal/pick for collapse clearing/something)
Never remove or leave unloaded/in disrepair: Melee, Midranger, Bandage.. so, 2?