Advice request -- feasibility and licensing for personal website with subdomains

Soon, I plan to host a website with two or more distinct sections using subdomains that will set the document root for the subdomain to a subdirectory of the shared hosting account, such that the domain reviews.mysite.domain will actually be located in a sub-directory ../reviews.

I want to use Perch for at least part of this overall multi-subdomain website. But I'm not completely clear where I should install Perch -- obviously it depends on whether I'm using Perch for the whole website, or just one of the subdomains. Would there be problems or extra configuration difficulties if I published Perch for only one subdomain, considering that the subdirectory is technically considered to be the document root? On the other hand, if I published Perch in master root for the whole thing, could it handle the directory rewriting to the subdomains? Is that one thing that Runway can do?

The other concern is licensing -- would the multiple subdomains count as different websites for purposes of the license agreement? Does the structure of the installation and where the document root for each subdomain is located have anything to do with whether or not the different sections are considered different websites for licensing purposes?

I'm open to using entirely different systems for different subdomains, in which case I'll probably use my Perch license for one subdomain site. But I'm also open to using Perch or (more likely) Runway for the whole thing, if doing so seems reasonable.

Thanks for any input or ideas.