To move Add to Cart/Quantity under Product Title, you can use this code to Website Tools > Custom CSS.
/* product info order */
.ProductItem-details .ProductItem-details-checkout {
display: flex !important;
}
.product-quantity-input {
order: 1 !important;
}
.sqs-add-to-cart-button-wrapper {
order: 2 !important;
}
.ProductItem-product-price {
order: 3 !important;
}
.ProductItem-details-excerpt {
order: 4 !important;
}
Result
