I will say this: Agents will absolutely reject you if your novel is too long or too short for the genre you're writing in. No agent will take on an 80k MG novel, no agent will take on a 30k romance novel, or a 300k novel in literally any genre. If you're close to the expected work count, it likely won't make a huge difference, but if you're way over or way under, an agent won't touch it, because the work it'll take to get the book to a point where they are able to sell it may not be worth it.
While there are outliers (like The Notebook, although I'll also note that this book was published about 25 years ago and genre conventions change), a word count that is massively off the mark will often be an easy rejection for an agent.
As for the 60k question: You might get away with it if it's YA contemporary, but in any other genre, that'll probably be too short.