Cook the pasta: Bring a large pot of salted water to a boil.
Cook the pasta until just al dente according to package directions. Do not overcook, or the salad will get mushy.
Rinse and cool: Drain and rinse the pasta under cold water to stop cooking. Shake off excess water well.
Toss with 1 teaspoon olive oil to prevent sticking. Set aside to cool fully.
Prep the crab: If using lump crab, pick through for any shell fragments and gently flake apart. If using imitation crab, chop into bite-size pieces.
Make the dressing: In a large bowl, whisk Greek yogurt, mayonnaise, Dijon, lemon zest, 2 tablespoons lemon juice, Old Bay, dill, remaining olive oil, a good pinch of salt, and a few grinds of pepper.
Taste and adjust seasoning, adding more lemon or Old Bay as desired.
Add the mix-ins: Stir in celery, red onion, bell pepper, and peas (if using) until evenly coated with the dressing.
Fold in pasta and crab: Add the cooled pasta and crab to the bowl. Gently fold with a spatula to avoid breaking up the crab too much. If the salad looks dry, add 1–2 tablespoons of water or extra yogurt to loosen.
Chill: Cover and refrigerate for at least 30 minutes.
This lets the flavors meld and the pasta absorb some dressing.
Finish and serve: Give it a final stir. Taste again and adjust salt, pepper, or lemon. Garnish with extra dill or a sprinkle of Old Bay.
Serve cold.