1. Cut the tofu into 1-inch cubes. Transfer to a paper towel-lined plate and season with salt. Set aside.
2. Bring a large pot of salted water to boil. Cook spaghetti according to package directions until al dente, about 15 to 17 minutes. Drain, rinse with cold water and set aside.
3. Meanwhile, combine peanut butter, soy sauce, rice vinegar, ginger, garlic, brown sugar and 1 teaspoon chili crisp to a large bowl. Add 1/4 cup hot water and whisk until smooth. Add more hot water by the tablespoon as needed to create a pourable sauce.
4. Add spaghetti, tofu and snap peas to bowl with sauce. Taste and season with salt and pepper if needed. Sprinkle with crushed peanuts and chili crisp. Serve immediately, or refrigerate for up to 1 day.