Argo Smart Routing and Argo Tiered Cache

I have read some blogs saying that Argo Smart Routing uses Tiered Cache. But in Cloudflare doc it says “Using Smart Tiered Cache may decrease performance improvements from Argo Smart routing between the origin and upper-tier.”.

In the dashboard, I can enable Argo Smart Routing in Traffic > Argo, and Argo Tiered Cache in Caching > Tiered Cache. So I assume they are different. My questions are:

Is it better to turn on both Argo Smart Routing and Tiered Cache?
What happens if I turn on Argo Smart Routing and turn off Tiered Cache?
Thank you so much!

I have read some blogs saying that Argo Smart Routing uses Tiered Cache. But in Cloudflare doc it says “Using Smart Tiered Cache may decrease performance improvements from Argo Smart routing between the origin and upper-tier.”.

In the dashboard, I can enable Argo Smart Routing in Traffic > Argo, and Argo Tiered Cache in Caching > Tiered Cache. So I assume they are different. My questions are:

Is it better to turn on both Argo Smart Routing and Tiered Cache?
What happens if I turn on Argo Smart Routing and turn off Tiered Cache?
Thank you so much!