Re: Getting Started
Creating a network whether in subdomain or subdirectory structure won’t affect your permalinks per se. As per https://codex.wordpress.org/Create_A_Network it’s how your subsites’ URL’s will show up online. Remember, these are virtual subdomains, i.e., even with a network subdomain set up like http://subsite1.mysite.com, it will be set up in server with folder structure wp-content/blogs.dir/2/files/year-etc. unlike that of physical subdomains /subsite1.mysite.com/
Network title is the title of Main site. As for subsites in subdomain/subdirectory it will be what you title each one and the default description would be something like “Just another [title of main site] site.”
For more assistance re multisite installations, please post at the WP multisite forums https://wordpress.org/support/forum/multisite
