I need help setting up search console better for multiple subdomains

Hi,
I have a cms-type service where everyone that signs up gets a subdomain where they can see the output files generated by the cms.

I'm currently adding all subdomains of my customers as a property to google search engine and submitting a sitemap, so my customer's content gets indexedfast.

Do you guys think this is a good way to handle my customer's SEO? I'm a bit out of ideas how else to accomplish this.

Thanks