Hi there!
Generally we do not provide support for custom CSS Code. However, making an exception to align your express buttons on checkout page, you can use this following CSS code.
@media only screen and (min-width: 60rem){
.woocommerce-checkout .wc-ppcp-express-checkout {
vertical-align: top !important;
}
}
Issue regarding add some space between add to cart button and pay with link button you can use the following css code.
@media only screen and (min-width: 980px){
.single-product div#fkwcs_stripe_smart_button_wrapper {
margin-top: 10px;
}}
I hope this helps.