Saying this as both an Outlast and Mouthwashing lover.
A lot of people in the Mouthwashing fandom would not be able to handle it in the Outlast fandom, especially when it comes to liking characters.
Especially on tik tok, it seems the Mouthwashing fandom is so strict with what it does and doesn't allow, like I hate Jimmy as much as the next guy, but it's not a crime for someone to draw him or include him in the cast. He's an IMPORTANT part of the plot. The tik tok fandom also seems to say Mouthwashing shouldn't have a fandom point blank period because it's "too deeply thought out" and fanfics, ocs, and such shouldn't exist because it "ruins the story".
Meanwhile Outlast is a horrific, well thought out game with several installments, and the fandom is (mostly) chill. Like it's abundantly clear these guys aren't good people or even conventionally attractive to most people, yet they're adored and people make silly jokes of them all the time and make tons of fanfics, aus, and ocs. Hell, 90% if the fandom's favorite or second favorite dude is a guy who cuts people's dicks off and then kills them.
This isn't meant to say you can't have boundaries or things you like/dislike, but much of the Mouthwashing fandom overpolicies the fandom, and some even say Mouthwashing shouldn't have a fandom period because it's "too serious and dark" while Outlast is serious and dark yet no one cares what you do in the fandom.
Both are horror games with great stories.
Both produce gorgeous fanart and deep theories, and it's clear love is put into several art pieces and theories.
Difference is, a majority of one fandom can't handle fandom ACTING like fandom.
(Mini edit: Honestly this could be about fandom as a whole nowadays but given they're both horror games, albeit different types, with fan bases, that I love, I decided to compare them. Lets try to be civil please)