Definitely use a child theme!
Quark was well designed with child themes in mind.
These are tips, how to deal with your concerns about styles and functions.php files:
"e.g. it requires 2 x style.css (parent and child) and sometimes, overwriting styles is cumbersome and creates extra code which wouldn't be required by using starter theme in standalone."
Keep styles.css empty in a child theme. Enqueue parent styles.css in child's functions.php with the following code:
add_action( 'wp_enqueue_scripts', 'wpse_child_theme_scripts' );
function wpse_child_theme_scripts() {
wp_enqueue_style( 'parent-theme-css', get_template_directory_uri() . '/style.css' );
}
Use Customize - Additional CSS to override parent's styles and to add new CSS rules.
"The same goes for functions.php - quark loads 2 x google fonts - if i dont use them and load my own google fonts, i end up loading resources that are superfluous."
As I mentioned before, Quark, being well designed, allows overriding parent theme functions in your child theme. To load google fonts on your own, put the following code in child's functions.php:
function quark_fonts_url() {
// your code to load fonts goes here...
}
Parent's function quark_fonts_url is a pluggable function, so it will be replaced by your function, declared in child's functions.php. Only your fonts will be loaded.
There are many pluggable functions in Quark. You can override them in your child theme, if you want to change their functionality.