Can URL remain the same if migrating from Drupal?

yes, but: it might be hard if drupal mixes several types of content under the /node/ parent. Those are not very SEO or even human freindly URLs so you might actually want to change them and just have a redirect from the old one to the new one.

Site broken after using URL Change in Admin

Best way If you have access to the site via FTP, then this method will help you quickly get a site back up and running, if you changed those values incorrectly. FTP to the site, and get a copy of the active theme’s functions.php file. You’re going to edit it in a simple text editor … Read more

How do I override the emoji url?

Looking at the code, you should be able to filter it. Something like the following should do it: add_filter( ’emoji_url’, ‘wpse_232874_emoji_cdn_url’ ); function wpse_232874_emoji_cdn_url( $url ) { return ‘http://example.com/my/cdn/url/’; } …replacing http://example.com/my/cdn/url/ with whatever URL you want to use. Reference Plugin API

Remove / from www.example.com/ [closed]

This isn’t a WordPress thing, this is a browser/HTTP thing. Firefox may be showing the / as part of a setting, but example.com and example.com/ are the same URL. This Q on webmasters goes into more detail as to why this is the case: https://webmasters.stackexchange.com/questions/35643/is-trailing-slash-automagically-added-on-click-of-home-page-url-in-browser