Iron Farm Beds

building up my iron farm, but i cant remember some specific mechanics

1. Ik the beds have a golem spawn range of 16x6x16, but does that mean i have 2 or 3 vertical spawning blocks above the bed?

2. i’m aware that i need at least one villager to ‘detect’ the beds, but i don’t know what the ‘detection’ range is?

i’m just trying to get a quick and dirty farm up, no trading or fancy storage system