Brew the tea base. Bring 4 cups of water to a boil, remove from heat, add tea bags, and steep for 5 minutes. Remove tea bags, squeezing gently to extract flavor, and allow the tea to cool completely.
Prepare the peach component. Add peaches to a blender with 2 tablespoons of honey or simple syrup and blend until completely smooth. Strain through a fine-mesh sieve to remove any pulp or skin if desired.
Make the raspberry puree. Blend the raspberries with 1 tablespoon honey or simple syrup and the lemon juice until smooth. Strain through a fine-mesh sieve to remove seeds.
Sweeten the tea. Once the tea has cooled, stir in the remaining honey or simple syrup to taste. Remember the fruit mixtures will add sweetness, so you may need less than you think.
Assemble in glasses. Fill tall glasses halfway with ice cubes. Pour the tea until each glass is about half full, then add about 2 tablespoons of peach nectar to each glass.
Create the layered effect. Carefully pour 1-2 tablespoons of the raspberry puree over the back of a spoon held above the glass so it floats on top of the tea-peach mixture. This creates the beautiful layered effect.
Finish and garnish. Top with a splash of sparkling water if using. Garnish each glass with fresh peach slices, raspberries, and a sprig of mint if desired. Serve immediately or refrigerate for up to 24 hours.