How powerful is your system? Many people with low-spec systems report choppy playback in preview, usually, but not always, when filters have been added.
See here on how to report errors so people have a much better chance of helping.
With an i7 processor, you shouldn’t be having problems with choppy audio. One suggestion - check you haven’t got 2 instances of Shotcut running. SC goes very slowly if you have. It’s easily done if you double-clicked when you started SC.
I have only one instance open and I shut down all other programs while using it. The strange thing is that I can bring in MP4 files and the audio in those files plays back perfectly.
I think I may have to just live with the quirk for now. I’ve only used this program for one day but I think it’s a great program and I will continue to use it.
Never been a fan of mp3 format.
Have had too many problems with strange bit rates, latency and hate that small bit of silence at the start and end of many mp3 files.
Since you have Audacity, why not convert to PCM(WAV) or something like FLAC if WAV creates files which are too big.