1. In a shallow glass baking dish, blend the soy sauce with the mustard and sugar. Add the salmon and turn to coat. Refrigerate for 2 to 3 hours.
2. Light a grill. If using charcoal, scatter the wood chips and herbs over the coals. If using a gas grill, place the wood chips and herbs in a smoker box or scatter over the heat bars. Place a large double layer of foil over the center of the grill. Arrange the salmon on the foil. Cover the grill and smoke the salmon until just cooked through, about 10 minutes.
3. In a large bowl, mix the mayonnaise with the lime juice and season with salt and pepper. Gently fold in the radishes, cucumbers, avocado and onion.
4. Using thick oven mitts, carefully lift the foil from the grill. With a thin spatula, transfer the salmon to plates and serve with the avocado-radish salad.
Make Ahead: The hot-smoked salmon can be refrigerated overnight.
Wine Recommendation: The salmon's smoky flavor and its pungent marinade suggest an aromatic, fruity white, such as a Pinot Gris from Oregon. Consider the 1999 King Estate or the 1999 Willamette Valley Vineyards.