I believe you get increased API throughput on the Plus plan. Details are included here --> https://shopify.dev/concepts/about-apis/rate-limits. Basically if you control the code that's performing the API requests, I'd build in a sleep routine so you stay within the limits.
I would closely reference this documentation and like already mentioned, add some throttling if your app hits that rate limit often. Implementing throttling using the same leaky bucket algorithm Shopify's APIs adhere to is quite simple though I'd add some "wiggle space" i.e. buffer to be safe.