Fascinating! I literally never use Claude without plan mode and I find it's basically useless without it, constantly wasting tokens going in circles on irrelevant things. Fable or Opus. I feel like neither has a good sense for how to architect things and if I don't use plan mode it usually wastes hours of time chasing it's tail or implementing kludges on kludges to get something working that would be a much simple fix elsewhere, especially when working on a larger codebase.