It's nearly 3:00PM at my time and there doesn't seem to be more information about the upcoming Closed Beta next month, so I hope they'll disclose what you're going to do in the Beta, like whether or not you have to use a new character or not, or most importantly that this is PC exclusive not PC and X-Box exclusive. I can already imagine some people preparing to sign into the beta using X-Box only, so I hope they'll make very clear disclosures when they come to sign in. Especially about whether or not you can bring your current character and gear in there.
Normally I do expect there'll be automatic rejections if you're signing in the wrong way or won't be able to complete the sign in if they don't have the required specs or was expecting to sign in using X-Box One or Series X. Just because it's part of Windows 10 on a technicality doesn't mean that's not what they were wanting to test at the moment as theorized by Anamana. But the opt out option I'm hoping for, but more hopefully not needed, is what you're going to do in the Beta and whether or not you can bring your current character, just to repeat myself. And... I guess that was pretty much the point of this thread.