But to give a very quick summary the game they were obviously building was supposed to build up to the whole "eldritch horror" aspect of the story. The player was originally an explicit foreigner to the city of Yharnam who came or was brought there by his friend(named but I cannot recall the name right now) for treatment. This is still partly true as the armor description for the default gear insinuates this but the illness not so much although NPC still talk about some thin-blood or some such(its been too long since I played so I do not remember all the terms exactly). The friend however got completely cut as he was supposed to be revealed to have turned into the Cleric beast but most likely much much later than right after the boss fight.
I assume this because the entire area of Old Yharnam and Djura is all about revealing that the beast are in fact people a plot twist that is not a plotwist because its explicitly told to us right at the start of the game. So Djura even making a fuss about it is in the final game a plot hole but in the "alpha"(no idea why they call it that when its a feature complete build 6 months removed from release) story this probably made complete sense. You can further observe bits of this original intent in Upper Cathedral Ward which in the released game is for some reason trying to freak out the player with a
chandelier set piece accompanied by the most basic werewolf enemies who at that point are complete pushovers. But in the "alpha" upper cathedral ward was most likely a much earlier area, possibly filled with friendly NPCs that were later meant to turn into beasts and this was supposed to be the "oh shit" moment of the game.
Further more the game was obviously made with some time of the day/night mechanic as the game does internally track what part of the game the player is in but does nothing with it otherwise. However based on the alpha its clear that Yharnam was supposed to gradually get more beast infested as the night progressed as there as spawn triggers link to the time of day. Most likely even the beastly Yharnam people who in the finished game are the default enemy and ergo spoil the whole "the beasts are people" were most likely meant to show up later into the game when the hunt actually began.
There is more but I have other things to do at the moment so the best I can do is refer you to the links I posted.