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The thing that defines ramen, is not the soup, but, the noodle. Both the Chinese, who invented them, and the Japanese use alkaline noodles. Done right, these noodles will not soften in broth for a long time. They have a distinct yellow color and a firm texture. Generally, if you are using alkaline noodles in Japan, and putting broth over it, you are making ramen.

Pho is about the broth, you want a clear broth, and again, it will generally be more salty/savory than anything else. Heat is generally added as a condiment, either as sliced chile added at the time of serving, or chile oils added when the broth is added over the noodles, or at the time of serving.

Oh, something I recently had that was truly delicious, was a Hot and Sour soup poured over fresh wheat noodles.