How can I track subdomain acquisitions?

My property has multiple subdomains and each subdomain has it’s own view. I have Tag Manager setup to use the same cookie for all the domains, but I have not yet added the subdomains to the referral exclusion list.

The reason being: I want to be able to track the subdomain "referral" traffic. I want to be able to look at a user’s journey across the subdomains in a single view. If I add the subdomains to the referral exclusion list, they’ll be lumped into the "direct / none" acquisition category without a way to differentiate them, correct?

Will I get duplicate data if I let GA record the subdomains as referral traffic, but I have the auto-cookie feature enabled in GTM? Has anyone found a workaround for this dilemma?

Any help/guidance/suggestions are more than welcome!