Internet was my prime consideration as well, and all of those places have excellent internet. 20+mbps 3G/4G mobile internet at reasonable prices on top of solid connections at most hostels and airbnbs you could stay at there.
Rural Taiwan is especially nice because you're just a high speed rail ride away from Taipei, most likely. The others would probably involve a cheap and very short flight to the nearest metropolis, in case you miss the city life.
Okinawa can feel a bit touristy, but you can get away from it if you do some groundwork.
I spent a month out of an airbnb in Krabi town. Lived for about $200/mo, spending weekends doing touristy things and eating out most of the time. I got familiar with just about every shopkeep and restaurant owner in the hood. Random streams and gardens to hang around in and pass time and ponder the universe. I enjoyed it, and miss it sometimes, but the place helped me discover that personally I am a city-junkie and needed to get out of there.