1.EMS and DHL my experience with both have been equal so far...both took similar amount of time to reach my house..
if the area that u stay have bad pos laju service then DHL might be a better choice(? not confirmed just taking a wild guess)
anyway when u choose shipping method amiami will show the shipping fee that u need to pay..and of course u will choose the cheaper among the two

2. paypal is just another payment gateway nothing special about it..
u create a paypal account and link ur credit card with the account to pay
be careful though as there are two choice for exchange rate used one is paypal's rate the other one is ur credit card issuer's rate (u need to compare and see which one gives better rate)
I think someone here once said the difference in the exchange rate between paypal and ur CC issuer are too not big of a difference

3. I dont remember using paypal to pay amiami for first time purchase..might be policy change?
Have been using my credit card to pay for long time