For the soundtrack are you talking about how Yamamoto got caught plagiarising and they had to switch out all of his stuff for Kikuchi's, but didn't have access to all the Kikuchi music so had to overuse some tracks? On streaming sites this only becomes relevant post-Namek at some point from what I've seen - on disc I guess it'll depend on when the discs were burned (early copies will have Yamamoto for at least Namek and I think Android/Cell, later ones will be fully replaced with Kikuchi). Like watching Kai on streaming sites, it uses Kikuchi's music for Trunks vs Freeza, but without the unique Trunks music, since they didn't have access to it I guess - I honestly don't mind the Kikuchi music they've put in for him attacking Freeza, although it does stop awkwardly. I don't remember finding Kai's Kikuchi music bad when I watched up to Trunks vs Cell.
I think the Japanese VAing in some bits is a bit better in the OG. Like I do prefer Nozawa's kkx4 in the OG over the Kai one (happened to watch both two days ago). Kai's SSJ1 transformation doesn't do the deep voice. Krillin's VA when dying is a tiny bit more harrowing in OG I think too. But I might prefer Nozawa in Kai for Gohan's reaction to Piccolo getting Freeza-beamed (for the VAing itself, but also OG does some washed out effect on the voice when Gohan is crying out).
Comparing Yamamoto to the OG's Kikuchi, I'm not sure which is better. I think Kai is a bit more dramatic for Freeza returning and beaming Piccolo and Kaio's reaction (no music in the OG. Also lol, in OG there's a 2 second still frame of Yamcha etc staring at Kaio at the end. I thought the video had frozen). And better for Vegeta vs Recoome. In Kai it starts to feel like the fight is on straight away after Piccolo gets beamed, while OG feels like an intermission period, for better or worse. Krillin getting killed probs prefer OG very slightly. Going SSJ1 it's the OG hands down, this one is not even close lol. The second half (post-adverts) of Gohan beating up Freeza gets my adrenaline going more in the OG. Kai generally seems to use dark pieces less, like for that scene and for SSJ1.
Honestly the OG is just too fucking long lol. Like how can a one minute scene turn into five minutes? Move over NASA, turns out Japan invented time travel in the 80s.