For the most part, the English endings were pretty faithful to the Japanese versions, but I found some interesting points that were either lost or ambiguous in the English version. Because of the way the languages work, the Japanese version can fit more info than the English version can. So most of the paired ending changes amount to having an extra sentence or so.
Tana and Cormag - The Japanese version has an added detail that Cormag quickly became Tana’s close aide after he was knighted into Frelia’s service, and she placed an enormous amount of trust in him.
Joshua and Natasha - JP version states that the reason why the nomadic Joshua stayed put was because he had a beloved wife at home. But nothing changed his gambling addiction.
Joshua and Gerik - In terms of the ending, it’s not much different. But it details that in Jehanna’s prosperous years after Joshua’s rise to the throne, Gerik was always by his side.
Eirika and Seth - Their ending in the JP version makes a bit more sense than the English one, given the context of their A-Support. Seth was opposed to the marriage between a royal and her vassal, but with Ephraim’s matchmaking and Eirika’s strong will, he decided not to suppress his feelings anymore and agreed to marry her.
Franz and Amelia - It details that their daughter had Franz’s faithfulness and Amelia’s cheerfulness. Also, it’s implicit in the English version but the JP version explicitly says that their daughter served in Renais’ army.
Vanessa and Innes - Vanessa and Innes became lovers and were never married (English version just says that she moved into Castle Frelia, JP version explicitly says she moved there to be Innes’ 愛人, which means mistress/lover). When they had a child together, nobody kicked up a fuss and their child was regarded as a blessing to all, so possibly Innes never married to begin with (or Frelia has no stigma against these things).
Garcia and Ross - Ross’ son’s favorite phrase was “I want to be manlier than even dad and grandpa!”
Kyle and Lute - The biggest change I’ve seen so far. The “and Kyle dedicated himself to his [son’s] upbringing” doesn’t exist in the Japanese version at all. Instead, it takes the “Lute studied their son’s baffling habits” line that’s also in the Artur-Lute ending.
L’Arachel and Innes - Like Seth-Eirika, this pairing makes more sense in the JP version. It explains that because of their constant attempts to outdo one another, sea trade between their countries flourished like never before. And then they fell in love.
Gerik and Tethys - Details that the two were perfect partners, and they lived happily ever after. (This “lived happily ever after” appears a lot in the JP FE8 paired endings.)
Myrrh and Saleh - At first, the villagers wanted to worship her from a distance, which made her withdraw from them. Saleh served as a mediator and communicated her feelings to the villagers.
Ross and Amelia - Also ends with Ross’ son’s favorite phrase, but without the grandpa part.
Innes and Eirika - The feeling of the ending is a bit different. Unlike the English version where she “acknowledges” her feelings for him, the JP version uses the same language as with Seth in his ending with Eirika; she couldn’t hide her feelings for him anymore or she realized just how much she liked him.