You may want to do the Xfce 4.16 Tour. A lot of changes are documented in the changelog. The release announcement tells most of the changes and why. You may want to read also the Roadmap and the reasons behind the switch to CSD. After looking at it again, it was one of the best decision by XFCE team to do it. I would even liked they did the full switch IMHO.
People who dislike it, may use libxfce4ui-nocsd in combination with gtk3-classic packages.