The theme supports custom css, you can override anything you want by redefining classes in the assets/custom.css file.

For instance, changing the main width can be done as follows:

:root {
    --main-width: 1024px; /* overrides default of 780px */
}

Note that backward incompatible changes in the CSS will likely not happen, but there might be cases in the future where backward compatibility is not possible. If you are overriding a huge amount of CSS I suggest you forking the project instead of defining it here.