i think 'psychological horror' has to touch on less literal or obvious or physical threats to focus on the existential implications of whatever horror phenomena. even if there is a literal physical threat like in silent hill, the themes focus on things like the fallibility of perception and epistemological uncertainty about what is going on. you don't just fight monsters in a silent hill game, you fight the environment, you fight your own character's perception of reality, mostly safe abandoned rooms transform into rusty bloodsoaked horror dungeons, the people around you are often untrustworthy and just as dangerous as the monsters, no one knows why any of this happened in the first place and there really isn't a coherent scientific explanation.

compare the above example of silent hill to something like Resident Evil or the film Dawn of the Dead. Both resident evil and dawn of the dead do use their settings and lore to address more fundamental issues, but this is only via metaphor, and usually points to something less existential and more sociological or political. RE and DotD both have more or less scientifically plausible 'zombies', that the characters more or less understand as a mundane physical threat like a natural disaster or a terrorist attack. the existence of the horror elements may cause them to question society (consumerism in DotD, rampant military-industrial complex corruption/dysregulation/corporate terrorism in RE) but not reality or their own minds. its more of a sci-fi intrigue or a post-apocalypse scenario than a mind bending psychedelic terror experience.

Subnautica exploits your fear of open ocean. Almost all the "horror" is basic survival instincts (don't drown, don't get eaten), limited view, and a deliberate design choice by the devs to not put weapons in the game. Various "monster" games, like Alien: Isolation and Amnesia follow this formula.

Silent Hill games like to mess with your sense of space by constantly changing the interiors, messing with your unconscious gamer modes (mapping, treasure hunting, etc). Alan Wake follows lightly in this space. My House mod for DooM is designed to specifically to subvert the Doom experience.

EDIT: Subnautica also did something subtle: the game mechanics are easy and forgiving on purpose. Fauna clearly indicate when attacking, the big fauna shake you around for a moment the first time, you don't drown until well after the timer hits zero, damage isn't all that bad, etc. The game is littered with these kinds of "threats" that, from an objective standpoint, aren't that threatening. But how these design choices are presented gives the player the impression that they "just squeaked by" a deadly encounter throughout the game.

Psychological horror focuses on the horror brought on by psychological abnormalities. e.g. the world shifts around the protagonist or follows dream logic, it's revealed that they've been an unreliable narrator despite being the player avatar, heavy themes of guilt, shame, loneliness, trauma, etc.

It's usually a quieter and more subtle horror, and more inclined to use "fridge horror" -- horrifying concepts that don't quite hit until you think about it a bit. The appeal of it all is that the threat doesn't just come from outside -- it also comes from your own head.

If we're suggesting movies...

Triangle

Possessor

Amulet

Infinity Pool