New project or new subdomain?

I have a site that serves three sets of cohorts or groups:

  1. Public visitors
  2. Artists
  3. Nonprofits

The public visitors will interact 90% of the time through a mobile device. They will access the site via a QR code typically in a public setting and not in their home or with a laptop computer. So the “app” is or should be the default site

Artists and nonprofits, on the other hand, will access the site via a home or business computer. Probably through an email link or search bar. They create and update the site content.

It is cumbersome to say the least to create one platform or website that hopes to accommodate all three groups with adaptive design.

It makes more sense to create a default site with “mysite.com” or “www.mysite.com” that receives 95% of the web traffic and then a subdomain like “admin.mysite.com” to focus on the needs of desktop users - artists and nonprofits.

Distinctions will be evident how content is displayed probably in a grid. In the default site the grid will be one column for phone or tablet portrait mode. The admin subdomains would offer the same content but in a two or three column grid so the content can be easily edited.

So there is identical content in the default domain and the admin subdomain, but the CSS and page layout will be different.

How should I proceed making this happen? Do I:

  1. Duplicate the project so make modifications to the css that does not create conflicts with the default domain. I am assuming this is necessary and the right way forward. Or
  2. Create a subdomain and let it go at that

Hope my questions are clear.

You might be able to find your answer in this post Subdomain & different site