Welcome! I have also tried to maintain a level of credible doubt in the divine in my writing. Certainty is rarely as interesting as doubt for an old cynic like me, so I have deprived my characters of this received wisdom. What motivated the idea of having heaven and hell be the same place, for you? It reminds me of Zach Weiner-Smith's idea of a "polystate", where multiple fashions of citizenry can share space but now jurisdictions. I guess it's a bit like the fediverse too, eh?
I've played a lot of RPGs in my day, and every time the most boring thing that can happen (enemy is killed) is what the mechanics always most strongly support. Pairing an elaborate system of thin escalation with a highly lethal combat system (that being Greg Stolze's Reign) is how I hope to see more fisticuffs, dance fights, rap battles, structured duels, and sporting wagers between enemies than fights to the death. So I haven't given as much thought to afterlives as I eventually want to.
My setting has an "otherworld" where souls can reside, but no "heaven" per se. The forces of evil there are all just nature spirits that oppose the solar deity, and operate in many ways to undermine the sun god. The otherworld is a metaphysical no mans land that has been overrun by sentient fire and beings called elves that we would more likely describe as cenobites. I was thinking that there should be a "Valhalla" style afterlife where souls of knights are sent there on errantry to try and kill demons, but that hasn't been implemented yet.
I'm drawn to these choices because I am trying to accentuate conflict in as many aspects of the setting as possible, in a way that makes room for more than simple "violence to the death" encounters. I've written many rich cultural traditions and social mores into the lore and game mechanics all structured around measured escalation so that characters in my stories can make a conscious choice about how to handle an adversary and to maximize the survivability of antagonists.
Edit: Sorry for the wall of text by the way, filthy habit.