Solution:
To remove login form from Woocommerce checkout use:
// Remove login form from checkout
add_action( 'woocommerce_before_checkout_form', 'remove_checkout_login_form', 4 );
function remove_checkout_login_form(){
remove_action( 'woocommerce_before_checkout_form', 'woocommerce_checkout_login_form', 10 );
}
To remove Registration from Woocommerce checkout simply use:
add_filter( 'woocommerce_checkout_registration_enabled', '__return_false' );
Both snippets goes in function.php file of your active child theme (or active theme). Tested and works.