How to make www.mywebsite.com and secure.mywebsite.com only on ONE webflow project?

I have the following

I need the following:
www subdomain for most pages, landing page and seo contents
secure subdomain for funnels,

I need to split funnel steps and transaction funnel pages

Example: checkout step 1>
goes to secure.mywebsite.com

blog >
goes to www.mywebsite.com

I want to duplicate the site across both www. and secure. subdomains, but set up rules on a PER PAGE basis

Normal Page = www. subdomain
Secure Page = secure. subdomain

^
Is solution for custom code per page?

I’m guessing you’ve seen this Connect a subdomain | Webflow University

If so, the only way I can think of to point a subdomain to a page is to point it with the A record in your domain registrar to forward to any page you like.

So correct me if I’m wrong, but it sounds like you need separate site plans for subdomains because they have to be separate projects?

I believe so if you want to do it on the Webflow side. But any registrar will allow you to point any subdomain wherever you want.