I have been using SharePoint for over 10 years and just recently took a job using SharePoint online, what interested me was the interface but I am finding myself struggling with some of the basic functions. In the older versions it was easy to get to edit WebPart settings. In SharePoint online finding that I can even figure out how to move a webpart to a different zone or even increase the size. Any help would be greatful.
Controlling the layout is something you cannot do OOTB in modern SharePoint. If you want to overwrite any existing layouts, you need to inject script/css using extensions.