I am currently assisting in the organisation of React London 2017, a conf in London for around 600 people. We are working with an events company who are doing a lot of the heavy lifting, but it has given me a better idea with what to expect.
While I haven't organised many events exactly like this, I have done a lot through roller derby that has given me an appreciation for the complexity of running events such as this. We did everything from a mixed team game to a 3-day bootcamp and that involved all the same challenges presented by this, such as finding a venue and sponsors, and ensuring that the event was adequately staffed.
AlterConf was a traveling conference series that provided safe opportunities for marginalized people and those who support them in the tech and gaming industries.