Line two small rimmed baking sheets with parchment paper.
In a medium microwave-safe bowl, combine 1 cup of the chocolate chips and 1 tablespoon of the coconut oil. Microwave until just melted, about 1 minute on high. Stir to combine.
Holding one taco shell from the inside over the bowl of chocolate, use a spoon to spread the outside with melted chocolate, letting excess chocolate drip back into the bowl. Repeat with remaining shells and melted chocolate.
Arrange on prepared baking sheets and freeze until chocolate is hardened and chilled, at least 10 minutes.
Using a serrated knife, slice the ice cream crosswise into thin rounds. Cut each round crosswise into strips. Keep ice cream frozen when not using.
Working with one coated taco shell at a time, remove the shell from the freezer. Fill halfway with ice cream. Spread fudge over top. Return to sheet tray in freezer. Repeat with remaining coated taco shells, ice cream, and fudge. Freeze 1 hour until fudge is hardened. Freeze filled taco shells until frozen and firm, at least 2 hours.
In a medium microwave-safe bowl, combine remaining 1 1/2 cup of the chocolate chips and remaining 3 tablespoons of the coconut oil. Microwave until just melted, about 1 minute on high. Stir to combine.
Working with one filled taco at a time, spoon the chocolate sauce over the top of the ice cream, completely covering the ice cream. Sprinkle with either half the peanuts(¼ cup), half the coconut flakes (¼ cup), or half the sprinkles (1 tablespoon). Arrange finished tacos standing up on the parchment lined baking sheet (use small bowls or measuring cups to hold tacos up). Repeat with remaining tacos, chocolate sauce, and toppings.
Freeze filled taco shells until frozen and firm, at least 1 hour.