If you create a private page and post devlogs on it, those posts will not be publicly available. Your other option is to create an empty project page and then start publishing devlogs there. Note that empty project pages on itch.io don’t gain any visibility in our discovery systems, so you would only collect viewers through your followers, visitors to your profile page, and places where you shared a direct link to the page.
Another approach I recommend is using the Posts feature available on your dashboard. You can access this here: https://itch.io/dashboard/posts. You can write posts directly to your account without the need for a project page.
Once your page is up, you can use the “Convert to Devlog” button located at the top of the post’s edit page to reassign that post to another project page on your account.
Hope that helps