I recently worked on a project which needed me to shut down a WordPress blog and migrate it’s content. I had about 20 posts and pages that were going to migrate but everything else was going to be deleted. Since htaccess runs their commands from the top to the bottom, place your known redirects above your catch all redirect.
# redirect the posts and pages that moved - list all known urls below
Redirect 301 /known-path/ https://www.newdomain.com/known-path/
# Redirect everything else to the new domain homepage
RedirectMatch 301 ^ https://www.newdomain.com/