If using metric, weigh ingredients for best accuracy.
In a stand mixer fitted with the whisk attachment or in a large bowl with a hand mixer, cream the solid coconut oil, room-temperature butter, packed brown sugar, and granulated sugar until smooth and well combined.
Beat in the eggs one at a time, then add the vanilla extract and mix until smooth.
Add the baking soda, salt, and cinnamon (if using), then add the old-fashioned oats and beat until just incorporated.
Gently fold in the all-purpose flour until no dry streaks remain, then stir in 1 3/4 cups of the chocolate chips.
Cover the bowl tightly with plastic wrap and refrigerate the dough for at least 1 hour and up to 3–4 hours.
Portion the chilled dough using 3 leveled tablespoons (about 70 g) per cookie and roll into balls; you should have approximately 20 cookies.
Preheat the oven to 350°F (175°C). Chill the rolled dough balls in the fridge for 5–10 minutes to firm them up.
Arrange up to 6 dough balls on a sheet pan lined with a silicone baking mat or parchment paper, spacing them about 3 inches apart.
Bake for 13–15 minutes, until the tops lose their gloss but centers are still slightly soft; this yields soft centers and crispy edges.
Immediately after removing the cookies from the oven, press the reserved 1/4 cup of chocolate chips onto the tops and tidy any edges with a metal spatula as needed.
Let the cookies rest on the sheet pan for 3–4 minutes, then transfer them to a cooling rack to finish cooling.