Jester David
Hero
I don't like the fact that you can't knock someone unconscious with a single blow (in RAW). If you can get yourself into the right spot (via stealth) you should be able to do it. It's a classic adventure move after all. My house rule: a strength vs passive constitution check. If strength wins (I.e. Force of the blow) then the creature is knocked unconscious. I'll give a PC disadvantage of the size of the monster is huge (or bigger)
If the monsters are bigger than the PCs (like bugbears) do they get advantage to knock out the PCs?