@elvenmystery well most professional writers post their stories here to build up a target interest before release. Sometimes Wattpad then backs them...tbh I don't really know how it works and I imagine both parties maybe benefit in some way.
Personally, I wouldn't post a whole novel, just enough of a set-up to get vital feedback and listen to how readers are interacting with the early plot and characters. It's also good to see what type of patterns emerge in terms of reader demographics then you can tailor the rest of your plot to that audience.
Lastly, nobody can steal your idea if you don't have your full novel on display. You know in your head what your draft looks like, as long as you don't announce that to the world you should be safe. The most someone could do is be inspired by what you've written and try something out, but actual writers would NOT steal people's work...wannabes do but don't worry about them professionals no the difference...and you can always address plagiarism with the website if you feel it's just.
Hope this helps! And I wish you all the luck in the world, mellon. I'm hoping to attend an event too, so I understand your concerns.