The U.S. Store will not ship outside of the U.S. Unless you intend to ship it to an address within the U.S. you won't be able to get it sent to you in the Caribbean.
If you are going to be sending it to an address within the U.S. and plan on using it outside of the U.S. consider 2 things:
- It will not have any warranty outside for the U.S. and must be returned to the U.S for warranty service.
- You do not need to choose any carrier. Unless you haver a number and account with one of those carriers you won't one able to choose the carrier. Choose the "Connect to Any carrier later" option instead.
For the payment plan, choose whichever works for you. That is a personal question. Only you know which payment plan is good for you. Also note, unless you are a U.S. citizen you cannot get an Apple Card and as such cannot use that payment plan.
For the carrier's payment plan, you must take out a service contact with the carrier you choose so you will need to have a U.S. address at the very least.