I'm not 100% what you're getting at, but TextEdit is for sure bad at reading encodings, as when I open a Shift-JIS in TextEdit it turns to mojibake. I do not believe Mac has a locale setting like Windows, which is an ongoing struggle for me and I end up configuring UTAU banks on Windows bc of it. Mac hates any language that isn't the one it was set up in, so tread carefully.
But the choppiness is likely from the Oto being unconfigured, which in short means.... they didn't oto the bank. Oto files tell UTAU the timings for files, so if it has the wrong timings, it will end up sounding bad. That is out of your control, unfortunately! You can Oto it yourself, but that's your choice. It's time-consuming, and quite the commitment for an UTAU that isn't your own.