City of Darkness might be a good fit, if you don't mind horror! It's a relatively new game so it's slow paced and small, and it is backtag friendly. Every time a plot post goes up we make a little section where players can plot with one another, plus I plan on throwing up a CR meme down the road for more plotting opportunities.

If you're interested, you can check out the game info on the profile and/or take a look at our current test drive! :)