German here. There are at least two major differences that stick out like a sore thumb.
The funny thing is that everyone automatically assumes it is the Japanese "thousand year old goddess in a child's body trope" ... but the crankend-up-to-eleven romance was ADDED in the English translation and they're still only pen pals in the original. An analysis from reddit that I blatanly stole:
I think this whole quest is very interesting, but I just can't get behind it, because the context of the quest is so drastically different in the japanese version and english translation.
It starts with finley calling the letter "love letter" in the english version, while in japanese it's just a plain old "メッセージボトル" "letter in a bottle". That's a HUGE diffrence.
Then there is the option "A letter?" when you speak with finley after she has thrown the letter inside the river.
In the english version she goes on and on an and on about, how wonderful that guy must be and how she hopes, that he is as wonderful as he describes, all in a very lovestruck way. Then she says something that's not even present in the japanese version. The whole thing about her concerning herself with him being okay with her being older, wiser and a Zora girl and talking about keeping an open mind when it comes to love, is not present in the japanese version. She never says she is older or wiser and she never mentions anything about love. The conversation ends with her saying:
"「筋肉ムキムキの冒険者だ」って お返事には書いてあったのですが
いつも繊細な文章なので きっと素敵な方なんだろうな って思うんです"
translating roughly to:
"He wrote "I'm a very muscular adventurer" but his writing is always so delicate, so I think, that he must certainly be a very wonderful person"
That's where the japanese one stops.
Now we come to Sasan. There are also some glaring changes to his dialouge, that change the whole context of the quest, which in general is: Finley's parents always being busy and her being lonely, wanting to find a friend. That's what one can infer from her second option of dialouge.
Sasan also calls the "love letter" "letter in a bottle" in the japanese version. He also refrains from calling Finley a "lovely Zora" and just says "The sender seems to be a female Zora named finley".
He is also not "dying to meet her" he says "だから 会いに行きたくてもどにも腰が重くてね・・・" "Even if I wanted to meet her, I'm a bit hestitant...", in reference to him lying to her.
The text after that is radicaly different as well. In the english version he is devestated, had he known, he would fall for her, he never would have lied to her. Link supports him saying "Love reigns supreme".
In the japanese version he says "しまったなぁ こうなるなら 嘘書くじゃなかったよう・・・" "Now i've blown it. If I had known it would come to this (this being her wanting to meet him), I would have never lied..."
Link supports him saying "心が大事" very roughly translating to "Your inner values matter", because the concept of 心 is very broad in japanese.
And while he says, in the japanese version, he will run all the way to the Zora domain for a little bit of training, he doesn't mention trying to get really really buff on the way for her.
He just wants to start practicing what he preaches in the japanese version.
When talking to the two in the village, that's the first time the two texts kind of resemble each other. Finley does indeed call Sasan her "運命の人" which can be translated as "Soul mate". It could hint at her really thinking of him in a loving way in the japanese version, even if that was not established beforehand, or it could, more likely, reference the folk tale that says that if a person finds her letter, she will have great luck her entire life, kind of hinting again, at something more romantic. Even then, those hints are really subtle and could be seen either way, them being friends, heavyly implied, or them becoming lovers, very very unlikely but still subtly implied.
That's where the similarities start and end, as, shortly after that, Finley tells Sasan to work out for her, because he has promised HER muscles after all. In the japanese version she says "ササノ君! 泳いだり ガケ登りしたりして もっと筋肉モリモリになってね!"Sasan! You have to swim and climb more cliffs, so you become more muscular, 'kay!", again, she kind of says that because the two of them want to go on adventures, so it kinda makes sense, why he has to become a bit buff.
Sasan's answer to that marks the final big difference. While in the english version he wants to try his best for his "darling" (Finley) in the japanese version he just says "う うん・・・がんばるよ・・・" "m...mh... I will try..."
I think it is very interesting to see, that the Tree House of America choose to kind of take those subtle hints, that could be seen as something romantic, ran with it, but then always came back and justified it, like with Finley and Sasan HAVING to mention that she is sooooo much older and wiser than him. I personally don't have something against the "old soul in a child's body trope", but I generally assosiated it as japanese trope and was shocked to find out, that, in this case, it's an english plot line exclusive. Make of that what you want xD
Other comments also imply that the romance is absent in the spanish, french, russian and italian versions, but since I speak neither of these languages fluently, I can not personally confirm anything.
Him teasing Link falls into that category as well, but not because he wants to belittle Link and stroke his own ego, but because Revali thinks that Link, too, just takes for granted that he has a cool powerful sword and doesn't seem to have any motivation to use its full potential.
His dialogue isn't hurtful or condescending at all. It's more of a "we are a team so please start to pull your own weight already instead of relying on others all the time" thing. A little frustrated at times, but overall supportive and loyal.
There are more examples like these but the comment is already way too long as it is, so 'Ill be leaving it at that.