I think you won’t get a better forum than bitcointalk, however, you are looking for presale and upcoming project discussion. I'm not sure if any other forum has such discussion. It would be better if you look at the upcoming ico websites though they are very biased. Other than that, you can follow some telegram groups which sometimes share such projects which they think good.
It's true that this forum is the best I know, many people even talk about altcoins.
Usually I know that from various social media groups including Telegram which also allow their version of the best altcoins, even with new projects that are coming there are always discussions there, maybe we ourselves do good research or not.
When it comes to a valid forum, of course Bitcointalk.