since you asked for metanarrative questions: what medium (book, comic, tv show, movie, theater, video game, or any i missed) do you think would be the most bearable / workable to be a self-aware character in? and which would be the worst?
took a couple days to answer this because I've been busy and wanted to give the question a good amount of thought, but I think that a lot of it depends LARGELY on how closely a meta-aware character would still have to stick to their script. would you be able to just freely move within the world as you chose? or would you be stuck having to spout the exact same lines and same actions, fully knowing that you're a character in a work of fiction, but unable to alter your situation at all? or somewhere on that sliding scale?
put more simply, knowing you're a fictional character would suck ass regardless, but if you had a high degree of agency within your medium, at least you'd be able to figure out something to make your existence more pleasant. conversely, I think any medium, no matter how light the genre you were placed in within the medium, could be hellish if you were completely denied autonomy outside of your preset "script."
all that said, assuming the same degree of autonomy across every single potential option, i would DEFINITELY pick cartoons as the most bearable place to be a self-aware character. it's already somewhat established in cartoons that characters can screw around with the fourth wall - bugs bunny does this frequently, for instance. there's a lot of fun and silly shit you could do in that medium, and since cartoons are frequently light in tone, you wouldn't be in too much danger of being stuck in a horror story. would probably still suck, obv, but you could at least have a little fun with it!
i may be a bit biased because i'm a huge fan of deltarune's implicit Existential Torment, but i do think it would suck the most to be in a video game and fully aware of that. of course, a character in any medium or genre is very much at the mercy of the author and audience, but in a video game, you as a character would very frequently be at the mercy of a player. it's a much more direct form of power over you, and if you're an NPC who the player has the power to kill, that's real freaky. even if they can't hurt you, the effects of a player on the world of a video game are almost always REALLY huge, since video games are an interactive medium. it would be a little scary, I think, seeing the player character go around and do shit in the world you live in! i could handle the audience of a theatre or a movie or comic just fine, but gamers? nah. don't wanna be in a world where those are around.