For some purpose it is not necessary to use displacement that of course needs some performance. Instead of that you can use the normal-map which contains the same depth-information as the displacement.
Yes, at the moment we only use Paypal, but we will add stripe asap. That makes it possible to pay with creditcard and more.
We are working on that and we try to transport all userdata including the links for purchased products into our new shop.
If you find something inconvenient, or not working correctly, please report us. We want to provide the best user experience as possible and we are looking forward to your feedback.