The table below is a comparison of the models available. These will eventually all be available with built-in Bluetooth, in the meantime any that are not can add the Bluetooth Dongle to get the same functionality. In each case below the first number in the title is the maximum allowed input voltage allowed. This is the open circuit voltage of your panels, if they are wired in series add them together. The second number is the maximum allowable output current. How many watts you can use with any particular charger depends on what the battery voltage is, see below the chart for more details.
How many panels you can use with any particular panel depends on what voltage the battery is. With a 15 Amp charge controller you can use up to 200 Watts of panels in a 12 volt system or 400 Watts in a 24 volt system. In each case the output current is the same. You can use the formula Watts = Volts x Amps to work it out. They are using 13.3 volts as the actual charging voltage for the purposes of the calculation.
200 Watts = 13.3 Volts x 15 Amps
400 Watts = 26.6 Volts x 15 Amps
If you go slightly above the maximum allowed output current the charge controller will still work but only pass the rated current. If you used a 220 Watt panel in the example above you would still only get a maximum of 15 Amps
If you go slightly above the maximum allowed input voltage of the charge controller you will fry it. They recommend not going within 5 volts of the maximum.