See module web_editor for the editor code used everywhere.
All the editors in Odoo are based on Summernote, but the JS launchers (rte.js and ace.js — ace is used to edit code) try to not depend on it. In the web_editor module the views/editors.xml file will help you to understand the various JS files. You can alter the launchers or replace the xml view with a new one launching TinyMCE JS file.
You may find other modules code useful to help :
https://www.odoo.com/apps/modules/10.0/web_ckeditor4/
https://www.odoo.com/apps/modules/10.0/ckeditor_widget/
https://www.odoo.com/apps/modules/8.0/web_cleditor/