Are nodes performance tested before they are accepted on to the network?
Yes, all nodes - Stargates, Gateways and Hosts - are performance tested before they are accepted on to the network. The testing solution factors available resource, including bandwidth and latency.
The platform is location aware, both geographically and topologically. Hosts connect to local Gateways and Gateways to local Stargates, meaning that tests reflect local network conditions.
Testing happens over a period of time (short for Hosts, longer for Gateways and longer still for Stargates). Once a system is accepted onto the network there is an on ramp, a period during which requests are slowly increased (avoiding the risks associated with a flood of requests).