There is no difference between keyboard mode and the input method mode. Some keyboard mode will invoke the input method function and some will not. There are four keyboard modes:
This is to input the Alphanumeric characters. The Alphanumeric mode is exclusive with the Tsangjye mode and Phonetic mode.
This mode invokes the Radical input method, and the user can type in the defined radical character (a part or a component of a Chinese characters). The combination of these radical compose a Chinese character. When the user types in a radical, the candidates of this radical are shown. Normally, there are many Chinese characters that have a same radical, so the first candidate list includes numbers of characters and all of candidates can not be shown at once. If the user types in one more radical of the character, then the input method shows only the character that have these two radicals. The numbers of characters are smaller and get closer to the target character.
This mode invokes the Chinese Ping-in input method, and the user can type in a string of Alphabet, then press the convert key to convert it into a list of candidate. Select the target character like in other input methods. This input method is quite popular in P.R.C..