I am an English player on a Japanese-dominant JP server. I can't read or type Japanese apart from basic greetings. Rely heavily on my friends who could communicate with them. Going to share my raiding experience in the Japanese community!
Three of us English players have been raiding in Savage tier contents since ARR, apart from several patches which we took breaks. (started with a static but gradually became just three of us)
Since 4.0 or even 3.0, we do not have a static and RF. We adhere to JP community's norms since we very much like it there. So, no meta comp, no openly finger pointing (indeed, if we are displeased with the progress, we would call the next attempt as the last and disband afterwards).
We have seen both extremes from the Japanese players. Really good ones and suboptimal ones.
Skill levels apart, culture is similar. Aim to clear, no funny strategies. Stick with the mainstream macro strategy.
In our server cluster, there is Tonberry which is populated by both Japanese players and a huge presence of Asian players (English players). It is common to see RF parties having the description "JP only". In my opinion, due to both communication barrier and differences in attitudes. English players are very quick to blame players and calling them out in party chat, which isn't common in the Japanese community.
Cannot comment much about skill levels between JP and E in our cluster, since we mainly recruit only JP players (we were questioned numerous times whether party was JP only). For every 1 highly skilled E player we had come across, we met more less skilled ones relative to the same comparison for the JP players.
Regarding meta comps, I am a bard main, and I still recruit NIN/DRG for the 2nd melee slot. This is also true when looking at other parties, they don't typically restrict roles.
For a PUG party, I'm pretty happy we clear savages consistently during 3rd-4th week. Enjoy the progression in RF from practice, to aim to clear, to enrage experience, to fast clears. We don't see many incidents of players pretending to be ahead of the recruited contents/progression.
Something interesting: started seeing more of Tonberry E players selling runs. Doesn't exist in the JP community, which benefits other raiders in my own opinion.