Need some clarification on what means ‘friendly’, like do they accommodate foreigners well, do they speak a lot of english, do they have friendly overall people or what is it? I’ve been to all these places I guess I’ll rank it in order of how convenient it was for me as a foreigner to travel these places:
- Taiwan (ROC) – Most people speak English, the second most polite people next to Japanese, very accepting of diversity, the most open minded East Asian country
- Hong Kong (technically part of China) – English is commonplace, generally better manners than mainland, very tolerant of foreigners due to past history as a british colony
- South Korea – English is spoken by a majority of young people and most cafes/shops/signs will have English, decent manners/politeness, a lot of Western style bars/restaurants/etc due to USA influence
- Japan – most people do not speak English well, most shops/cafes/signs (except for subway) do not have english on them, a lot of places are surprisingly cash only, people are probably the most polite but very shy, you will experience a big culture difference
- China – most people do not speak English, very rare to find any shops/cafes/signs that have english on them, people generally do not care about you so you have to fend for yourself, very few Western style bars/restaurants/etc, you cannot use foreign credit cards in most places, foreign apps/services are blocked so you have to either buy a VPN or use a Chinese substitute in any case its horrendously slow going to any foreign website.
For me Taiwan was the most convenient and China was the least.