Fill a large pot with water, generously salt it, and bring it to a boil.
Add the dry macaroni and cook until al dente according to package instructions, stirring occasionally.
Drain the pasta in a colander and rinse thoroughly with cold water until the pasta is cooled to room temperature; set aside to drain well.
In a large mixing bowl, whisk together the vegan mayo, yellow mustard, sweet gherkin brine, white vinegar, garlic powder (if using), cane sugar, kosher salt, and black pepper to taste until smooth.
Add the cooled pasta to the bowl with the diced bell pepper, diced red onion, diced celery, grated carrot, and diced sweet gherkins.
Toss everything together until the vegetables and pasta are evenly coated in the dressing.
Serve immediately or refrigerate for at least 30 minutes to chill before serving.