Move oven rack to middle positions, and preheat the oven to 350° F. Line two baking sheets with parchment paper or silicone baking mats.
In a large bowl, whisk together flour, salt, baking soda, baking powder, and spices; set aside.
In a separate large bowl, whisk sugars and oil together. Add pumpkin puree and whisk to combine thoroughly. Whisk in eggs and vanilla until combined.
Sprinkle flour mixture over pumpkin mixture and whisk until completely combined and no flour streaks remain.
Use a cookie scoop with a 1.5-2 tablespoons capacity to drop dough onto prepared baking sheets, about 1 inch apart.
Baking 1 cookie sheet at a time, bake 10-12 minutes, or until a toothpick inserted into the center of a cookie comes out clean.
Remove from the oven and cool on pan for about 10 minutes. Transfer to wire racks to cool completely. Repeat with remaining dough.
In the bowl of an electric mixer fitted with the paddle attachment, beat butter until smooth with no visible lumps.
Add cream cheese and beat until combined. Add powdered sugar, maple syrup, and vanilla and beat until smooth. Be careful not to overbeat filling or it will thin out. If you think the filling is too loose, put it in the fridge for about 30 minutes to firm up.
Turn half of the cooled cookies upside down. Pipe filling onto the flat side of overturned cookies.
Place another cookie, flat side down, on top of filling. Press down slightly so that filling spreads to cookie edges.
Repeat until all cookies are used. If you’re using sprinkles to garnish, hold each whoopie pie in your hand and sprinkle the garnish in the crack of the whoopie pie and turn until all exposed frosting is covered.