Preheat oven to 350°F and arrange bread slices on baking sheets. Lightly drizzle both sides with oil and bake until crispy, about 10 minutes.
In a skillet over medium-high heat, cook bacon until crisp, then transfer to paper towels to drain, reserving excess fat in the skillet.
Massage salt into collard greens until softened, then add peas, bell pepper, scallion, and garlic, tossing to combine.
In a bowl, whisk together vinegar, thyme, mustard, honey, Cajun seasoning, salt, and bacon fat. Pour over pea mixture and toss.
Spread cheese on toast, top with pea mixture, and sprinkle with bacon if desired.