Will my A1549 iPhone work in Japan & Philippines?
Even if LTE doesn't work where you are traveling, the iPhone 6 model A1549 will work on the following 2G/3G/4G network frequencies.


UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz)
GSM/EDGE (850, 900, 1800, 1900 MHz)
LTE (Bands 1, 2, 3, 4, 5, 7, 8, 13, 17, 18, 19, 20, 25, 26, 28, 29)


Your phone is unlocked, so any carrier's SIM card will work and you can connect to WiFi to download the latest carrier settings that will properly configure the radio for all deployed cell towers and frequencies that the handset can communicate with.

So, your question basically boils down to picking a price point and picking a specific carrier with coverage where you actually will be traveling. The good news is you can get a cheap SIM or two and then pick the one that works best to reload data and minutes once you know more about the conditions on the ground when you arrive.

My experience is the specifications are very conservative and you end up getting better/faster/more LTE coverage than is advertised as every carrier that can support iPhones gets more revenue from travelers even if the handsets in that country are sold primarily the device that speaks all the frequencies of the A1549 as well as it's own. I would love to be in on the marketing and engineering talks that led up to choosing models, but can only guess being on the outside of Apple.