Shamelessly bringing up PMD role-plays again because I just can't get enough! It would be a fairly relaxed RP, but with mechanics/a small plot to start with so it doesn't have to be completely sandbox. Actually, maybe it's a totally free-reign RP where members can come up with their own quests/mini plots at their own pace, and JP with each other that way (some world-building will already be set as a guide, of course). But also important - there is the option to go solo, too. I know solo posting in an RP kind of defeats the point because it's meant to be social lol, so I'm in the minority who prefer it, but when you're stretched for time/energy then it's good to have a solo journey to fall back on. Keeps you writing and relaxed!
+1 for a Pokémon Ranger RP, too!
For a non-Pokémon RP? Well, I like RPs that are meaningful to me and my interests, so I'd be happy for all sorts of video game RPs, potentially! The most important thing for me is that any member can pick things up again and keep writing even if the plot slows down, or others are busy.