How would I go about having my device, ESP32-C3, use older firmware like v4.3.7? Is there configuration changes that can be made in PlatformIO to help with this?
You mean ESP-IDF v4.3.7, i.e. this? That version is not listed in the registry. So you would need to fork the ESP-IDF repo, add the package.json to the 4.3.7 branch (see C:\Users\<user>\.platformio\packages\framework-espidf\package.json) and reference it in the [platform_packages] as framework-espidf, possibly along with downgrading to an older compiler. You can see the basics of that technique in the docs and the example