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.
This particular method gave a higher chance for investors to enjoy the benefits, Binance brings good success when the coin start the IEO using this exchange.
There are many traders and also investors who awaits this kind of opportunities, and once the token start the sell process those who've got the chance really managed to double or more their initial funds, (most of them)