Do I need Oxygen?
You don’t need Oxygen if you just want to change the styling of content generated outside of Oxygen (for that you can use MT). But, if you want to create content with drag and drop, you do need to use Gutenberg, Oxygen, or another page builder, because Microthemer doesn’t handle content generation – just styling. Also, you need some way to add your own custom classes if you’re following the system shown in the videos. And you do that via a content editor, not MT.
How to do the things shown in the video in MT?
The CSS side of things can be done in MT of course. If you want to copy and paste some custom CSS rules (provided by the two articlesassociated with those two videos), you can do that in MT via View > Full code editor.
