Without understanding much japanese myself, asking an AI to translate seems to be pretty accurate as far as I can tell, if you take the time to explain context and tweak it a little by asking questions.
It's kinda complicated since japanese has a different sentence structure than english so often translation simply can't be 100% accurate and sound like what someone would say in english, but since the AI can explain every word and why it did what it did, you can direct it to make something more literal or more natural and stuff like that or make it explain it to you and you can then tell it if it makes sense or not what it did and it will try to fix it if it doesn't.
Basically what matters is how much work you put into it. Something fully automatic like whisper(the translation part, those AI don't do transcription as far as I know) will be a lot worse than giving some context information to an AI and feeding it all the lines and if you take the time to do each lines one by one and question the results, I think you end up with something really good(depending on how accurate the transcription was obviously).
I've been meaning to do a comparison with a fully whisper translation and just transcribing with whisper and doing the translation with an AI line by line for a movie that had about 100 lines of dialog, but who knows if I'll actually get to it. I have the files, just gotta work on it.