Dunk only, I gave up splitting years ago. When I was young, I vacillated between the twist and slide.
Now for the dunkers, to what depth do you dunk? For how long? Single dunk or double dunk?
I dunk the entire cookie using chopsticks and eat in 1 bite. Approximately 12 second submersion time
I like to dunk for as long as possible.
Back when I still ate such sugary things, my routine used to be to pour a large glass of milk for dunking. I'd take 3 or 4 cookies and drop them in the milk before I started dunking. That way at the end when I drank the milk down the bottom of the glass was filled with soggy Oreo. That was my favorite part.
Chopsticks is one technique I never considered. I like your style!