Is any reason for me to withdraw coins from ICO account? I'm not planning to trade them for now and somehow I think they are more secure behind 2fa
As I have repeatedly said here
You can rest easy, because your Waves in a safe place on your ICO account. Later, you can use address from exchange where will trade Waves and calmly send your tokens directly to exchange.

sweet... what is: Please back up your seed!!! do I need own wallet for that?