Rowdy’s right
You don’t mention file codec, HD, 4K, etc. H264 files don’t play as well on some systems for example.
What drives, HD or SSD? That affects playback. Also try assigning your Cache to a separate SSD.
Clean the cache between projects
Set PP playback windows to 1/2, 1/4 resolution. That improves playback although not as sharp.
And remember audio files are tiny compared to video. I’d expect them to work better than video, esp with 64g ram
However system setup is the most important factor, then proxies if that isn’t sufficient.