I always wonder what is overseas spending. Does it mean I am physically overseas and swipe a card or does it also include stuff I buy online in other currencies (like books, software, whatever) from a non-HK merchant.

Seems like the best base rate for local spend is CX Amex which is $8/1 mile and best base rate for overseas spend is SCB Amex which is $2.5/1 mile.

Are there any annual fees related to SCB Amex?

I think I'm not going to renew my Amex Plat because it's a waste, I don't make my annual fee back in discounts and it's certainly not worth it for the miles. Not really worth it for prestige either, they're not difficult to get.