So im a bit new to minecraft or at least after basics. I'm building a mob farm in the sky and I had this idea of making a giant room with two blocks wide hole in the floor that is very deep and in the end there is hopper where all of the mobs land and eventually i come and kill them and the drop is gathered in a chest underneath the hoppers.
However i found two flaws in my build after i had completed it.
The first one is because my idea involved a water stream inside the giant room pushing everything towards the hole. But I can't calculate where to put the water and it became a pain to get rid of all the water with lava because i messed up that much. Is there any website or something that could help me calculate this? or is there a better idea you guys might have that doesn't involve many expensive stuff to make my build work. I am thinking of putting a villager on top of the holes but i really don't want to do unless im certain that it will work so let me know what you think.
The second issue is if I find a solution to the first issue, should i make it an automatic farm or an exp farm? im not sure which one to choose.
the dimensions of the farm i made:
30 x 15
H = 7
The hole is not in the middle however and the farm is in the sky.