Moving site from sub-domain to root

I’m just about to move a fairly hefty site from a client’s subdomain (blog.domain.com)
back to the root (www.domain.com). I regularly move WP between directories but I have a feeling this will be more complicated.

Found this suggesting I just move the index file:
https://www.ads-software.com/support/topic/moving-wordpress-from-sub-domain-to-root?replies=2

Is this the way to go? Or would it be better to change the settings/move the files?

Really appreciate any advice if you’ve done this before. Cheers