1. A little vague and hard to approach. Manga, just like western comics/books/movies/etc is such a broad medium you’ll always find something you won’t like. It’s pretty much a case of learning what to avoid.
2. Following from above, why? Because like in other types of media you can find some fantastic stories that might resonate with you. Or to engage with topics approached from a different cultural point of view. Or maybe just to enjoy the art. There are many reasons people love manga (and yes, stupid and/or fetishistic series are what some people look for).
3. I’d be lying if I said I’m knowledgeable enough to suggest some older classics. I’ll leave this one to the veterans.

Now onto suggestions…

I’m not familiar with Hoopla but here are two series found from a quick glance:

• A Silent Voice - story about bullying, repentance and healing. Can be pretty rough.
• Blame! - is a sci-fi series consisting of a lot of wordless walking through a deserted mega structure punctured by occasional fight scene. I don’t remember it being too edgy but it’s been a while since I touched it.

If you’re willing to check elsewhere, whether it would be on Mangadex or official apps, I could also suggest:

• Girls’ Last Tour - a post post post apocalyptic story about two girls traveling through ruins of a dying world. It’s a slower, contemplative series about existence and various mundane things humans don’t think about.
• Sousou no Frieren (Frieren at the Funeral) - one of the big ongoing series at the moment. A more… thoughtful (?) take on fantasy with focus on human relations. Limited action, big on joy of adventure and nostalgia.
• The Girl From the Other Side: Siúil, a Rún - story about a young girl living with a wendigo-like caretaker. Pretty unique art style.

I think these should be relatively safe to try out.

Edit: I’ve seen you mention being a christian and disliking some themes because of that. Is there anything specific you’d like to avoid?