Clashing subsites and pages

I asked this in the chat (apologizing for the duplication) but realized that perhaps it required a more thorough space here on the forum to solve the issue.

Wordpress Multisite allows us to create sites like example.com/subsite and example.com/userblog, if we set the Wordpress main site to example.com and happen to create the Page with URL example.com/subsite, how do we control Wordpress behaviour on how to prioritize where the visitor is being redirected?

Also, how do we prevent clashes between the blog example.com/subsite (works fine) and the blog example.com/subsite/another_subsite (does not work) which gives a 404 error despite all the database fields looking fine and the admin section being available?