I'm not ready nor have proper time to extensively delve into this topics but I really like this weekly worldbuilding discussions.
Kita people
the Northern part of New Delfos (Boyen Region and Delpho Region) is ethnologically relating from the RL lower Balcans and maybe Greeks and Turks, in a way, the Ottoman Empire.
Boyen people vs Delpho people - Boyen see Delphians as bigots that made everybody waste time with civil war and blame them for not uniting soon enough to fight Honto. They also see Delphians as too conservative or traditional, not as progressive as the northern alliance of cities that historically rebelled against the crown of "Delfos". On the other hand, Delphians are very cosmopolitan, they accept Boyens if they look like business people, they see normal Boyen people as proud workers that aren't historically entitled to rule themselves, every time they ruled themselves Delpho people had to intervene and ended up in war.
Kita vs Suna people - they historically ruled the southern people from Mahara and partially Kazjko. Their historical view of the people from the Suna desert (Mahara) as dirty barbarians that were easy to subjugate. This view hasn't improved over time since even during the Honto Expansion (RL WWII Japan) they were easily conquered (Resistance if futile, all your bases are belong to us, because they were left to fence for themselves).
Kita vs Seijin people - The Airanzu region and a partially Kazjko have a lot of Seijin people. They were always regarded as less advanced to the point of the Honto Expansion, they were utterly caught with their pants down. In modern times the Boyen region people (northern most) view most of the Seijin people with respect and like "corporativism" way of conducting business that this Boyen people think they lost with the revolutions and wars. But never be too careful with them, they can stab your back when you least expect. Delpho region people almost have a cold war with people from Honto (not all Seijin), They are like RL China looking at Japan, they cannot forgive the atrocities committed during the Honto Expansion, it's too recent and they feel they haven't been "compensated" enough.
World vs Kita - Kita are seen as the more progressive, safest people in New Delfos to deal with, they are the closest to other cultures and have the most historical and practical relations with Cefnorian nations.
Suna people
The Southeastern part of New Delfos (Mahara Region) is ethnologically close to the RL Middle East and Nothern Africa. They have interesting early history but they were subjugated and enslaved for a large period of time by larger Delphic powers. They didn't spread much in the Delphic bay due to Kita and Seijin "cultural pressure" but they are the most numerous ethnological group in Phoenixia. After the Great War they re-established a prosperous republic and were able to profit from the natural resources and post-war deals.
Kazjko Suna vs Mahara Suna - (UNDER CONSTRUCTION).
Suna vs Seijin people - (UNDER CONSTRUCTION).
Suna vs Kita people - (UNDER CONSTRUCTION).
World vs Suna people - Suna were commonly used as slaves or "defeated tribesmen enduring forced labor as repayment to war expenses" (AKA Slaves) for the Theocracy and then the Kingdom of Delfos. There is a sense of past injustice for inhumane treatment, yet they are still regarded as uneducated, uncivilized, easily dominated people.
Seijin people
The islands and some of the territories around the Delphic bay (mainly the Airanzu Region) is ethnologically close to the RL Japan. Setting the focal point of the Seijin in the Honto island, quickly allowed Honto to have control of territories nearby. Their early culture sets the basis for civilization in that bay but are regarded to have evolved very slowly and other powers took advantage of that to profit from their resources. As soon as the Khemish-influenced Suna people establish a strong civilization in the Delphic Bay they are no longer the main cultural influence. The rapid development of their industry and economy into the modern times opportunistically allowed them to control the majority of the resources of the Delphic bay.
Honto people vs the rest of the Seijin people - (UNDER CONSTRUCTION).
Seijin vs Suna people - (UNDER CONSTRUCTION).
Seijin vs Kita people - (UNDER CONSTRUCTION).
World vs Seijin - Seijin are regarded as exotic, tech-savy but also historically traditional. They will steal and improve all your technology, Honto high-standards industry allows them to coin "Honto Quality" value. Most Seijin in Phoenixia are seen as being descendants of ancient civilizations and rarely mix with other ethnicities. They can in a way be called racists for their traditional upfront politeness and business-like attitude but most of this cultures rarely include members of other ethnicities in their higher professions or company ranks.
To be continued/updated...