Argo Tunnels are most useful for security: you can serve HTTP from a server that allows no inbound connections. Or, you can use it to reliably serve a public site from behind NAT.

Argo routing’s ability to improve page load times depends on how international your user base is, and how poor your origin’s transit quality is. It’s great at improving the latency and reliability of a cheap host.

Argo is kind of an overloaded term... Argo (not tunneling) is better routing from the edge, which can have a measurable impact on performance. Argo (tunneling) can also impact performance in a positive way but it is also a nice way to secure things, provide access to secure/internal sites, provide ssh/rdp access into a datacenter, and other things.