Re: 2000 and newer
They are both the RC-51 over here. In euroland they were called the SP-1 and SP-2. They SP-2 has a few upgrades making it the more desirable version.
Same answer on the VTR. In the States, we know it as the RVT RC-51, Elsewhere, it is the VTR SP-1/2.
Honda just flat doesn't make their ECUs programmable. It can not be done, wrong hardware. You can buy the HRC versions that are programmable, but it is less expensive to buy the PowerCommander.
No, the PowerCommander doesn't act as a hard drive for the ECU. It lies inline between the ECU and the injectors and adds to or takes away from the amount of fuel the ECU tells the injectors to give.