I use Whisper AI's default setting and I use the mp3 ripped from the video (using VideProc Converter). On occasion I will up the volume on the video, save the new video and then rip the audio from the hi-volume video into a MP3 file. I'll sometimes do this when it appears that the video is low volume where there is missing dialog. I've also tried adjusting the default Whisper setting but haven't had any luck with that.
I will also try to find a "machine translation" from SubtitleCat. Then I decide which sub I think is better and use it for the basis of the new sub and use the other sub to provide clarity and fill in missing dialog. The real effort is in editing the subs post Whisper AI and SubtitleCat download.
The general procedure I use for editing is to first open the srt file in Subtitle Edit and run the "fix Common Errors" in the Tool dropdown. Then run Spell check and thn save the sub. Next I open the video on the left-hand side of the monitor and then open the srt file using notepad on the right hand side of the monitor and then attempt to edit the sub to match what is happening and who is talking. Correct pronoun usage and correcting for two many "I'm sorry", "I'm sleepy" and "comfortable" are examples where I feel need editing. It's by no means perfect, but what do you want for free?