*.saas.com is only used for the SaaS—no UGC (user-generated content)—e.g. the root is for the homepage, while help.saas.com for knowledge base.a.com/b.com redirects to saas.com a.k.a the homepage. Someday they might have their own landing page instead of redirecting.*.a.com and *.b.com are for users. They can pick anything e.g. bla.b.com as long as it's available, not used by other users.sub.myco.com.a.com/my-ucg. This is the default.saas.com, a.com and b.com are all managed in Cloudflare under one account (e.g. admin@saas.com).