I think you already mentioned all, of the common and most used methods to get funded, But sometimes crypto projects are just self-funded, and sometimes from VC or Venture Capitalist or from the private individuals, then the common practice the offerings. But for the safety, of funds, I will choose the IEO method if it was done on a trusted exchange like Binance.
it is the safest method I think. but seeing the success of the IEO is also not so great, even more, scam projects. then it is indeed better to join the IEO on a big exchange like binance. exactly as you said.
The first funding is the most central to start the project. therefore private sales which sometimes contain part of their own team are also important to take part in sales.