From Scrivener 2 to Scrivener 3 - Fonts in editor

I used Scrivener2 since 2013. Now I purchased Scrivener3, but i’m lot confused . The new version is very powerful, but it’s very different from the old one.
For example, with Scrivener 3 how can I modify the Fonts and the line spacing in the editor without to affect the fonts and layout in the output?

And, how can I reduce borders left and right in the editor?

Thanks to all

When you compile, you’ll see those preview tiles in the middle column. The default compile settings, particularly for upgraded projects, will state in grey text that “Main text formatting will be based on how text appears in the editor” (or the translation of that concept if you are using a localised version). If you see that then whatever you do in the editor will be compiled directly.

Try using another format, like “Manuscript (Times)”, you’ll note the preview tiles in that format change the font to Times New Roman and do some other formatting changes as well. As to how that works, right-click on one of those and “Duplicate & Edit”, then go into the Section Layouts area and click through those. That part there should be a lot like Scrivener 2. The main difference, specific to this question, is that each Layout can choose whether or not the text format will be changed. In version 2 that was just a global switch.

In the Appearance: Main Editor preference pane. There are margin settings at the bottom, and as well you might be referring to fixed width editing, which keeps the line-length static and pads the editor as necessary to do so.