Set EGG for direct cooking at 350°F/177°C.
Cut peaches in half, cutting stem end to tip. Remove pits and brush with oil.
Season salmon with salt and pepper and drizzle with one tablespoon of vinaigrette. Place plank on cooking grid, close the dome and heat for about 3 minutes. Flip plank, using tongs, and place salmon on heated side of plank. Close dome and cook for 10-15 minutes until salmon is medium rare. Remove salmon from the EGG, place green onions and peaches, cut side down on cooking grid. Grill until grid marks begin to form on peaches, about 4 minutes per side, and onions are slightly charred and tender.
Slice peach halves in half and roughly chop green onions; place in a medium bowl, tossing with half of vinaigrette. Serve peaches with planked salmon and drizzle with remaining dressing just before serving.
In a small bowl, whisk vinegar, olive oil, soy, honey, ginger, sesame oil, and red pepper until combined; set aside.