Why these together

Product teams need event analytics + planning + spec docs + user-research scheduling + survey response — and this stack covers all five with tools that integrate via webhooks without glue code. PostHog is the analytics surface (events, funnels, feature flags, session replay all in one) and replaces Amplitude + LaunchDarkly + FullStory simultaneously; Plane is the Linear-style issue tracker the engineering team will actually use; Outline holds specs, RFCs, and post-mortems; Cal.com schedules user interviews; Formbricks fires in-app NPS and targeted surveys keyed off PostHog cohorts. The realistic operational cost: PostHog wants a beefier VPS (~$20/mo on its own); the other four collectively fit on a $10 box.