Limit number of posts in loop

I consider the right way could be filtering of total number of found posts like this.

function my_custom_found_posts_limiter( $found_posts, $wp_query ) {

    $maximum_of_post_items = 100; // place your desired value here or read if from option\setting.

    if ( ! is_admin() && $wp_query->is_main_query() && $wp_query->is_post_type_archive( 'blog_posts' ) ) {
        if ( $found_posts > $maximum_of_post_items ) {
            return $maximum_of_post_items; // we return maximum amount, so pagination will be aware of this number.
        }
    }

    return $found_posts;
}
add_filter( 'found_posts', 'my_custom_found_posts_limiter', 10, 2 );

See source code here https://core.trac.wordpress.org/browser/tags/5.3/src/wp-includes/class-wp-query.php#L3234

and lines after this filter is applied to have better understanding of how it will work.

NB: I’ve used is_main_query() conditional and is_post_type_archive meaning it will be used for main Post archive loop or CPT archive page loop, but you can adjust the way you want.

UPD: added !is_admin() – check so it will not fire in wp-admin.