As long as the chunk is loaded, mobs will spawn
Meaning I can just chunkload the witch hut, but not need to clear out a silly radius around it? YAY 
Meaning I can just chunkload the witch hut, but not need to clear out a silly radius around it? YAY
If you find a way to chunkload the area to spawn mobs, which is quit difficult, I think.
If you find a way to chunkload the area to spawn mobs, which is quit difficult, I think.
Do normal chunkloaders not work? (Like world anchors)
Not entirely sure, and they may have changed it, but I think no.
That makes life harder 
I think it is because mobs need a player around to spawn.
There might be chunkloaders with fakeplayer but i'm not sure.
I think it is because mobs need a player around to spawn.
There might be chunkloaders with fakeplayer but i'm not sure.
Pretty much, I believe mobs will only spawn in player/fakeplayer-loaded chunks, there used to be a distance-from-player limiter that defines a "safe" area around the player that mobs could not directly spawn in.
Also, I'm pretty sure that there are a few chunkloader mods that use fakeplayer, but last I heard, there was a bug with it that either rendered it useless or caused a crash. The Forge devs have probably fixed it since, but do be careful.
Mobs can spawn everywhere, but they will immediately despawn in Peaceful or 128 blocks away from a player. They also have a chance to despawn between 32 and 128 blocks away from a player.
