What output power Dr.HDMI can supply ?

When used with a power supply connected to the USB, it will give as much as the power supply is capable.
When used without a power supply (powering from HDMI) it will give whatever it can take from HDMI connector. Usually 50-500mA.

How do you switch between Banks ?

There are a total of eight EDID banks inside the unit. When you press up or down button you can quickly move between any of them to select the desired one. Once you stop for a second or so, the system actually activates the selected EDID and starts the HPD (hot-plug) event. This is the event where Dr.HDMI will inform the source device that EDID has changed so the source must reconfigure it’s own internal settings. This takes about 2 seconds as per standards. During this time you will not be able to change the EDID. After HPD event concludes you are free to change edid again if wanted.
If you press the middle button, the display’s EDID is copied and placed into the EDID bank number 8. Once it is done, HPD event is also created and completes in about 2 seconds.