Moving WordPress and impact on SEO

I’m currently building out a replacement site for an existing site that gets lots of traffic. My dev WP site is in a subdirectory and not available for public viewing. Eventually, when complete, I’ll want the dev site to replace my currently site.

I’ve found the documentation that describes moving the WP index to root (allows most of the WP files to remain in subdirectory) but will otherwise appear as if the app is in my root (www.mydomainname.com).

My questions are… what impact does having WP in a subdirectory have on search engine rankings, if any? Is this the typical method for developing a replacement site? Does the SEO depend on the theme?

Thanks to all who respond.