Preheat an outdoor grill (preferably charcoal) for high heat and lightly oil the grate.

Cook bacon in a skillet over medium heat, stirring occasionally, until browned and crisp, 8 to 10 minutes.

Meanwhile, cut kernels from cobs into a large bowl using a sharp knife held at a 45-degree angle. Scrape cobs with the back of the knife into the bowl to release the juices.

Add 1/4 cup green onions (white and light green parts) and red bell pepper to bacon; cook and stir until vegetables just become tender, about 2 minutes. Stir in corn; cook until warmed through. Season with rice wine vinegar, olive oil, a few chopped dark green onion tops, 1 pinch cayenne pepper, salt, and black pepper. Remove from heat.

Coat both sides salmon fillets with vegetable oil; season with remaining 1 pinch cayenne pepper, salt, and black pepper.

Cook on the preheated grill until good grill marks appear, fillets flake easily with a fork, and salmon is still slightly pink in the center, about 5 minutes per side. Cracks in salmon flesh as you cook the fillets allows you to see doneness in the middle.

Divide spinach leaves between two plates; top each with a salmon fillet and 1/2 bacon relish. Garnish with a few green onion tops.