The model setting only sets the limits; it performs no scaling.
When you set the page size and scaling in Inkscape, it is editing how those parameters are set in the SVG file itself. Most important are the width, height, and viewbox parameters.
You haven’t said how you are creating the artwork. Normally, what you would do is to make the page the correct size in whatever environment you are using to create the artwork. If that’s Inkscape, you’ve already figured out how. If you are creating artwork in some other graphic environment, there are likely controls there to set the size. If you are creating things programmatically, you can edit how large the artwork is created within that process. And, if all else fails, you can edit the SVG directly within a text editor to set the size, or write a script to do so if you need to do the same thing repeatedly.
There is also a CLI tool called vpype that is specially designed to perform operations like this.
