i have been looking for the answer for months now
If you're not partnered and just use AdSense, Google will send a cheque through the mail. But, if a YouTuber is with a network, they can either get a cheque, PayPal or bank transfer.
Google adsense mails them a check. Many of them explain it in videos on their channels. It's not difficult to look up. I've even seen some of them film their checks to prove that yes, an actual check comes in the mail.