You got right answer from Spaceboy6, but ill also add a bit of unsolicited caution.
Even though there are few so called “fast levels”, it doesnt mean theres less stuff to learn in them, you are just not limited by radical completion so technically complete it in half the normal time.
Im one of those that slowed down after 30 (although be it not by much) and im really glad i did - not only are things getting more abstract - thus harder to remember, they are also getting rarer and rarer, meaning the benefit you are getting is not that big.
Well anyways you still have plenty of time till you reach 40s (where first fast levels appear), so youll see how you are managing before deciding, I bet youll have much more leeches than you do now, so you can decide then if (almost) double the reviews is something you can manage.
Edit: i do recommend reading the current speedrunning record holders celebration post to get better idea WaniKani World Record! Level 60 in 344 Days!