I can't speak as well to the horror genre, being more of an RPG fan myself. But I do have a suggestion.
In my time playing RPG games, I've seen a few that use horror elements to induce fear in certain scenarios. What I'd recommend is avoiding the typical walking-sim-in-a-dark-environment-with-jumpscares stereotype (You can still use these elements, just don't rely on them). Instead, use things like a loss of player control, unbearable / weighty choices, and imminent danger to push the horror feeling.
Here's an (entirely) sarcastic vid with some tips on what NOT to do when developing a horror game (and stuff that may help):
How To Fail At Horror GamesYouTube · Artindi156.4K+ views · 1 year ago