My core philosophy behind USMLE prep has always been do as many questions as you can. But I've had to come to terms with the fact that 2CK prep is very different from Step 1 prep. Kaplan I wouldn't recommend at all for 2CK. As I said, I did 2-300 questions before realizing it was a minutiae-joke once again. Ditching Kaplan for me was like finally blocking the psycho ex and feeling good about it. There was some question I encountered on SIADH, where it's exceedingly HY to know it's a euvolemic hyponatremia, but Kaplan had the answer as hypervolemic because they were talking about intravascular volume apparently. Either way, I was like, "Wtf would you ever write a question like that? Never in a million years would SIADH show up as anything other than euvolemia on the real deal." After I hit that question I ditched the QBank.
Uworld is good for 2CK, but quite a few of the questions (similar, but not remotely as bad as Kaplan) are tricks/train people to over-think, which I actually think is a big no-no. For example there's a question where the entire vignette is about a young vegan guy who has clear signs/Sx of B12 deficiency, and then the answer is pernicious anemia, not decreased B12 intake, because they say despite the veganism, pernicious anemia is more common. Then they went on to specify a technicality about the length of time he was a vegan and how that wouldn't have been long enough for B12 deficiency. Regardless, I've written several feedback comments to UWorld questions along the lines of "why are you training people to over-think? The NBMEs would never trick a student like that." That was probably the worst question I've encountered in UWorld so far.
But anyway, to answer your question, USMLE Rx I found to be solid for Step 1 but just OK for 2CK. I would not recommend going to USMLE Rx after UWorld. Rx isn't nearly as updated. I would recommend to any of my future Step 2 students to do Rx then UWorld if they are far from the exam. But if they are within the final few months, just do UWorld thoroughly and well and reference UpToDate.