Created a Volume on Big Sur and Now my MacBook Air is Slow

I was looking to play a 32bit game on my Macbook Air (early 2015) running Big Sur, so I researched on how to create a new APFS volume and installed Mojave.

Now that I've done that my Macbook Air is running very slow, the CPU usage is nearly topping 100% most of the time, idle 4-7% even when I shut down all my applications. I use my computer for work to have video calls and it's so slow, it takes so much time to load and even if I don't use my trust webcam app it's still running incredibly slow.

I still have over 16Gb of free space on my container. I've deleter a handful of top-tier tasks that were using up the CPU in my Activity Monitor, then I restarted my computer and it's still running slow.

I don't know what to do. I'm thinking of wiping my computer clean and reinstalling from my backup. Should I? If I wipe everything clean and reinstall Mojave do you think that will help, or is there something else I can try before resorting to that?

Any help is appreciated, thanks.