It's worth a read of the data sheets, as it gives a lot of useful information:
Forwarding rates are in the data sheet but they vary per model and are based on 64-Byte packet sizes.
Answering those questions is going to be difficult because as always, 'it depends' is the answer.
Certain types of latency are fixed based on the interface type and speed but other latency varies on the utilisation of the switch for example.
What type of hosts are going to be connected to these switches?
Just end user hosts or are they going to be used as Data Centre switches?