Just to add, I've match FPS of the sequence to my source files - I read that somewhere that it might help. I also tried converting the WAV tracks to MP3.. it has helped a very tiny bit but the problem is still there.
do not convert wavs to mp3's. mp3's are heavily compressed, and require more processing power to decompress. Are you saying you have multiple angles of 4K footage? If so, 16 gigs of ram is probably at least part of the problem and I don't think there's anything you can do about that. You might try a proxy workflow which will take a great deal of the computing overhead away. And you're not telling us the format of the 4K material. If it's mp4 or avchd, that requires heavy processing power to play back in realtime.
Thanks for the reply. Just for further clarification:
2x 4K MP4 video tracks (with one embedded audio)
2x WAV tracks (converted to MP3 temporarily for testing purposes)
1x MP3 track for very low level background music
All of them stored in SSD.
So additional RAM.. got it
Interesting your comment re: MP3 because its definitely improved playback from complete stuttering and constant dropping to at least now I can review footage 5-10 seconds each time before it start having any issues.
The MP3 background music, actually, keeps playing longer than the WAV.
It can't be simply the file size - I'm editing a 50GB+ file for another project and have had no issues...? Its only one big video file admittedly.
I think the issue could be the Intel Iris Plus Graphics GPU, it is low in VRAM and you are working with quite heavy files, also as mgrenadier says you have not given us the specifications of the container and codec of the clips.The SSD might be fine but it doesn't just depend on the transfer rate.The cheapest solution could be to work with Proxy's and in the end you replace the heavy clips before exporting.