Are Chinese and Japanese characters decomposed the same way?
Almost all Japanese characters (in my experience >99%) are exist in Chinese. Few are changed a little, like 宮 and 宫. As a Chinese, I have no difficulty in recognizing Japanese characters.

Some of Chinese characters is simplified in simplified Chinese, but remain unchanged in Japanese, like 車 and 车.

There are some rare Japanese characters which doesn't has corresponding Chinese character.　But they are still formed by components used in other characters.