I've been my own manager more than once and on teams from a few folks to a couple dozen in size. Rigid schedules and expectations absolutely make me less productive. My last 2 startups were chock full of fast paced, high quality work that got us off the ground and up to hundreds of thousands of users with me as the single engineer building apps for web, iOS and Android by myself. That is, until we hired engineering managers who tried too hard to get a glimpse inside my head, after which productivity dropped off a cliff. My current startup now has around 10 app devs and it feels like we deliver fewer features over longer timelines at a lower bar for quality than ever.