For the expected performance numbers we generally recommend that you speak with your Sales team. They are the ones with that information.
As far as tracking your TPS there are a couple of ways to do that. First you can enable statloging in the statlog.ini file, just set enable = 1 and restart radius. This will create a .statlog file that has statistics about SBR, including rate broken down by the job (auth, accounting, proxy).
Another way would be through the GUI, Go to Statistics>system and you can select Authentication Accounting or proxy from the dropdown. The average is a per second average of the number of transactions.
Finally you can enable SNMP and configure that to send rate statistic traps.