I built my own CMS system which places WYSIWYG content editor in a sandboxed iframe to avoid XSS. The advantage of this approach is that I can edit HTML directly using the browser's developer console in case the WYSIWYG editor does not support what I want. After all, raw HTML/CSS codes are behind what we see on a website, so I prefer to work with them directly rather than using Markdown. Whatever CMS you use, just make sure it supports changing theme/template and allows custom content to be inserted at different sections on a web page or preferably multiple pages (i.e global content widget). I found these 2 features crucial and make my work a lot easier.