Lag on Playback and Exported Media

I am working on a video project in Premiere Pro but the playback and export render quality is very poor. The footage lags all over the place and so do the effects on text items and clip transitions. I've checked my source footage and that doesn't lag, so I think it's something to do with Premiere. 

I tried a few recommendations online like giving Premiere more RAM and clearing media cache files and also pre-rendering footage in the editor. However none of these tips have really made a difference, and even the final exported video lags. I usually render in 4K (3840x2160) with an old preset I made when I created my first video. H.264, level 5.2 with high profile encoding. 

I am using a MacBook Pro 16" with intel which is relatively new. Rendering and handling this project shouldn't be an issue for it, and it hasn't been up until this project. The SSD is way less than 25% full. So I think maybe there's something wrong with the video settings rather than the laptop. 

I've attached screenshots of the project, and I am happy to provide more information if necessary. Thanks for reading.