Answer:
They are all very similar, and Korean and Japanese art is part pf the Sinosphere and they were heavily influenced by China.
If you don't know anything about them then they all look the same especially if there are no people or landmarks depicted such as on a decorative porcelain dish, and they all use many of the same ideas such as dragons, horses, cranes, Buddist symbols, stylized lions, kirins, pagodas, lotus flowers, cherry blossoms, and all those kinds of things.
Of course if there are people depicted, then regional fashions immediately tell you which culture it's from. And of there is writing, then that's also a very easy way to tell which culture it's from.
Chinese art thought still reflects idiosyncratic Chinese stories, themes, beliefs, ideas, and tastes. Common distinctive motifs include Ruyi, bats, lingzhi mushrooms, Chinese zodiac, Jade, Chinese gods, certain color combinations, certain subjects paired together, and certain objects and shapes.
Bonsai originally started in China as penzai, and then spread to other parts of Asia, and it's still cultivated by experts in China.
Except for bonsai, Japanese art very rarely uses those things. The dragons look distinctively Japanese, and so do the people. Japanese are also uses things like turtles, which as considered a bad symbol in China, and it's also fond of other animals such as crustaceans and koi fish. Japanese art is also fond of chrysanthemums, zig zags, and repeating geometric textile-like patterns. You will also see Japanese folklore and mythical beings and creatures unique to Japanese culture. There are tons of different mythical beings in traditional Japanese culture.
As for Korean art, it's more rare, but it also has its own, idiosyncrasies, motifs, and culture, and the Korean dragons look different, and the tigers look different.
