Can I Use a Custom Domain for My Psychiatry Newsletter?

Hello Hiiv! I'm starting a new mental health psychiatry newsletter and am on the Scale plan. Currently it's hosted on beehiiv https://psychiatry30.beehiiv.com and I'm also getting my office website updated: www.noesisclinic.com (current beta new site: https://noesisclinic.sysforte.com/ ). My question is can I do a custom domain: www.noesisclinic.com/blog which is what my webdeveloper is wanting in order to increase SEO and traffic to the main site. (When I look at this configuration, the main website (noesisclinic) header and footer crowd out the beehiiv header/footer.) In the Beehiiv helpfiles though it looks like this subdomain is recommended instead by beehiiv: blog.noesisclinic.com I do want to keep some separation so patients in the clinic do not mistakenly think that my newsletter is a private practice office 'news' letter for office updates. Couldn't the website developer just link the subdomain to my main website or SEO credits won't cross over? (I'm not that worried about the SEO as they are). P.S. Keyur P. I just signed up for unbeelievable to level up 🙂 Love the Canva Templates.