How-To Get posts with image & from specific Author at first of is_tax() page

Hello,

How can i do to have the post first result > Get Thumbnails && Author is not Admin

I did a first ‘pre_get_posts’ to have the none “default Thumbnails” on first results :

function filter_visite_with_image($query) {
    if ( is_admin() || ! $query->is_main_query() )
        return;
    if ( is_home() || is_tax() ){
	$query->set( 'meta_key', '_thumbnail_id' );
        $query->set( 'orderby', '_thumbnail_id' );
        $query->set( 'order', 'ASC' );
	return $query;
	}
}
add_filter( 'pre_get_posts', 'filter_visite_with_image' );

Maybe it’s not really code friendly but did the job.
But now, i want to have the ‘non-admin author’ first keeping the image filter…

Maybe be i can use this tutoriel : Modify Query based on Post Meta

But i don’t really know how to mix my old ‘pre_get_posts’ and this new tips.

Tell me if it’s not clear… (Damned Frenchy !)

Thanks for help

See you