50-100K is pretty standard for YA, though there are exceptions. I write fantasy and I personally aim for 60K for a MG novel and 80K for YA. When I was editing my MG/YA for submission, my agent suggested I keep it under 70K as a debut author.

It really has more to do with the pacing than the word count, though long word counts can get an auto reject if the query doesn't knock the socks off. Mostly because long word counts tend to signal a novel that's not ready and needs more editing. Pair that with a query that is overwritten and it's most likely going to be a "no thanks."

If the novel is paced well, hooks the reader and keeps them desperate to know what happens next through the entire novel, word count doesn't matter all that much. The longer the novel, the better the query needs to be IMHO, because you want to prove you don't waste a word and can use them effectively. You'd also want to show enough plot to say why you need all those words.

Longer books cost more money to print, so if you're going for a tradition publishing deal, that's something to consider. Publishers might think twice about spending more on a big book than a smaller one. If they're on the fence about it, a high word count could push you over it.

I feel it's a good idea to stick with traditional word counts as a first-timer to stand the best chance. No reason to give yourself potential negatives before they even see the story. I'd say keep it under 90K, but I'm sure you'll find plenty who'll give you a different number.