What are the differences between udon, soba, and ramen in terms of noodles and soup broth?

Let's put it this way, you can imagine these three brothers as people with completely different personalities.

Udon is like a gentle 'big white softy'

Noodles: Its characteristics are thick, white, and a soft yet chewy texture. Made from wheat flour, it's smooth to eat and very satisfying. The key is that 'bouncy' texture.
Broth: The broth is very light and elegant. Typically, it's a clear dashi (stock) made from kelp and bonito flakes, clear in color, and savory without overpowering the noodles. The noodles are the star, and the broth serves to complement them.

Soba is like a 'literary youth' with character

Noodles: Made from buckwheat flour, so they have a grayish-brown color. The noodles can be thick or thin, but generally thinner than ramen and udon. They have a unique buckwheat aroma and a refreshing, clean texture, less chewy than udon.
Broth: Soba is commonly eaten both hot and cold. When served hot, the broth is similar to udon's, also light. However, the most classic way to eat it is cold: chilled noodles are placed on a bamboo mat, and a special dipping sauce (called 'tsuyu') is served in a small cup. You dip a mouthful of noodles into the sauce, which is very refreshing.

Ramen is like an enthusiastic and uninhibited 'rock star'

Noodles: These are the most varied. Although also made from wheat flour, they contain 'kansui' (alkaline water), which gives them their characteristic yellow color and a very firm and elastic texture. They come in all forms: thick, thin, straight, or wavy.
Broth: The soul of ramen is its broth! The broth flavors are very rich, complex, and impactful. There are several main styles: the milky white 'tonkotsu' broth made from pork bones; 'shoyu' broth seasoned with soy sauce; 'miso' broth flavored with miso paste; and the clear 'shio' (salt) broth. Each bowl of ramen broth is like a work of art, accompanied by various luxurious toppings (chashu pork, bamboo shoots, soft-boiled egg, etc.), making it a vibrant experience.

In summary: