Shopify merchants can now control international pricing per region

Hello. Ok, so a few point to fully understand. I sell in Germany and Spain, different prices but same currency. Lets say I have product A that sells at 90€ in Spain and 100€ in Germany. My questions is:

a) my German customer will see the prices straight for them or is there a strange change in the payment gate? I presume that straight ahead they only see the German price if they are from Germany.

b) If a German customer buying from Germany wants to buy a product from spain how can I block the price so they don’t buy at a lower price? this is, German prices only for Germany, Spanish prices only for Spain and so on.

Thanks a lot