You can view the active folder format for the current window by opening Folder > Folder Options.
Folder Formats can be edited in Preferences via Settings > Preferences / Folders / Folder Formats.
Styles and Layouts (and Folder Tab Groups) can store their own folder formats which override the main ones (saved when you save the style or layout), but they have options to disable that.
Unless you actually want the Style or Layout (or Folder Tab Group) to change the folder format, you should tell them not to via the appropriate Preferences page for the type of thing (Style, Layout, Tab Group) you're using.
If you do want them to change the folder format, make sure the formats saved into them are correct. Load them up, check the formats, and if needed change the formats and resave the Style, Layout or Tab Group.
(Explaining this would be easier if we settled on a particular thing, but I'm not sure which thing you're using or having problems with.)
Format I now understand and I understand what overwrites what. Thank you.
To make things easier, we could settle on my favourite that was mentioned in my original question. I have tried to achieve this but I am not sure if this is a style or a layout. Please just assume that I know nothing about this.
Layouts can store the lister's size & position on the monitor, which is perfect for multi-monitor setups.
When I started using Opus I relied heavily on Styles, nowadays I don't use them at all. I use Layouts and Folder Formats and a bunch of hotkeys to tweak the display to show what I need.
This setup has evolved over the years and still is getting fine-tuned.
You could use either. It really depends on how you want to use them.
Styles are usually used to change an existing window.
Layouts are usually used to open one or more new windows.
They both contain roughly the same things.
Note that if you just want to define how everything looks all the time, then you don't need Layouts or Styles for that. Those should only be used when you want to switch to something different to your normal settings.
For your normal settings, the Default Lister is all you need.
Your first bullet point ("two panes with tree to the left") can be set up by simply turning on the tree and second file display, and then saving the Default Lister.
Out of the box, the Default Lister is saved every time you close a window. But you can also use Settings > Set as Default Lister to save it explicitly, and that gives you the choice of turning off automatic saving (so you don't accidentally change it in future). The setting can also be reviewed under Preferences / Launching Opus / Default Lister.
Most of what you're asking about (columns and sorting) doesn't directly involve Styles or Layouts, though. The other 5 of the 6 bullet points are properties of the Folder Format. Styles and Layouts can contain/override Folder Formats, but if you just want the same format everywhere then you should not think about Styles or Layouts, and instead set that up as per the Folder Formats FAQ.
At the bottom of that FAQ, there's a detailed video which covers most of your bullet points, in terms of column sizing and what is shown and hidden when there isn't enough width for everything:
