For the vinaigrette: Whisk the vinegar, the mustards and salt and pepper, to taste, in a bowl. Slowly whisk in about the olive oil and until emulsified. Taste; whisk in a few more tablespoons olive oil, if desired.
For the grape salad: Prepare the grill for direct grilling.
Brush the chiles with oil and season with salt and pepper. Grill until charred on all sides. Remove to a bowl, cover and let steam for 15 minutes. Remove the skins and coarsely chop. Transfer to a bowl and add the grapes, chardonnay vinegar and olive oil. Season with salt and pepper.
For the chicken: Whisk together the apricot jam and vinegar. Season with salt and 1/4 teaspoon black pepper.
Brush the chicken on both sides with oil and sprinkle with salt and pepper. Grill until the first side is golden brown, about 2 1/2 minutes. Turn, brush with the glaze and sprinkle on the thyme. Cook until just cooked through, another 2 to 3 minutes. Remove to a serving platter.
To serve, top with the grape salad, then the watercress and finally the almonds. Drizzle with the vinaigrette.