I've mostly had 1x1s on Discord with my close friend (now ex-girlfriend) for about a year and a half now. I usually lead the plot with the most amount of characters and NPCs though it's always clear that she could take it in any direction that she'd liked. We've have had several 1x1s going at once in the past with similarities between each. Usually, it's characters or setting interwoven into our multiverse. We currently have one ongoing plot, Starfall, though it's on hold at the moment for a few reasons. And most of the reasons are me, admittedly.
Generally speaking, we usually discuss our concepts beforehand and plan out characters, even ones that'll appear later, from the start. We do alright though usually stray after a few months into the project and get bored only to abandon it. My best friend from high school and I also have a 1x1 that we've been doing since 2017. This has been mostly been "on the spot" plotting and it mostly focuses on character development or world lore. We've had retcon things here and there, but we aren't writing professionally, so I don't worry about it too much. We started on the days of Skype and have since switched over to Discord. We also met in our math class which is always funny to me!
As for on the Guild. . Eh? I've been invited to a few 1x1s here and there, but my partner(s) have been dipping or there's been a radio silence between us. I had one Roleplay that I was in the process of writing eleven characters for, but then my partner left all of our DMs and hasn't responded to my Discord message. I've been working on a 1x1 interest check too, but uh. . It's
very slow going.