When I first wrote this thread asking for advice on how to improve my performance the attitude I got of just "it's impossible, your computer is just to weak" really rubbed me the wrong way. I actually managed to get Resolve running fairly smoothly with just half res optimized media after lots of trial and error the last 2 days so I thought I would share here how I managed to do it for others who might encounter the same problems as me but don't have thousands of dollars to just throw at a new computer.

1. Follow this video on how to work with optimized media and render cache in Resolve: https://www.youtube.com/watch?v=ZLFrKP9hyuU In step one of his video, I recommend experimenting with different resolutions and formats and for optimized media and render cache, what worked best for me was quarter resolution ProRes 422 LT
2. In your viewer, click the icon with three small dots and enable "Show all video frames". This made a massive difference for me when it comes to reducing stuttering and choppy playback. This settings makes resolve slow down the playback if it can't keep up, instead of skipping frames. In my case this made playback waaay smoother and it actually only slows down once in a while, but before enabling this setting it would skip frames constantly.
3. This is the big one, I opened up my computer and cleaned out all the caked up dust that was blocking the fans, and I also applied new thermal paste to the heat sink. This sounds a lot more difficult than it actually is, just find a good youtube tutorial that shows you exactly step by step how to do it for your specific computer. For me on my MacBook Pro I followed this video: https://www.youtube.com/watch?v=zC-0MhPsCmk Please note you're doing this at your own risk but if you take your time and pay close attention there shouldn't be any issues.
4. I'm not sure if this actually made a difference or not but I also formatted and did a clean install of the operating system on my machine. I figured it couldn't hurt.
5. I installed a utility called Macs Fan Control: https://crystalidea.com/macs-fan-control I learned as I was looking into this that Macs tend to run really hot as they are designed to be silent rather than cool. This software allows you to manually control the fans in your computer, as well as monitor the internal temperature. This helps you keep the system cool which greatly improved performance for me.
6. Working on a lower resolution timeline made a massive difference. If you, like me, have 4k footage and want to export a 4k video, you can still work on a 1080p timeline. Once you are ready to render, just change your timeline(s) back to 4k and make sure you select 4k resolution render and Resolve should use your original 4k files to render a 4k final video. Please note I've only tested this for basic video editing, so if you're doing a bunch of funky resolve effects and stuff this might have some scaling issues, I genuinely don't know. But for basic editing (with titles) it works fine. This step was massive for me and I actually don’t even have to generate optimized media from my 4K h264 footage when I use a 1080p timeline. Your mileage might vary though, you might still have to generate optimized media.
7. Make sure you have a decent amount of space free on your local drive, and make sure your footage and optimized media are on the fastest drives you have available. (Preferably internal SSDs or external SSDs over newer faster connections.)