I would schedule your CDCA a day or two after your NBDE just to get it over with. The CDCA is much easier imo and they reuse a lot of old test questions. Study for NBDE using dental decks / mosby's. Some people liked the app but I never used it and I felt like I left the test thinking I got probably 85% of the questions right where people that only used the app said they felt like they failed. Running through the decks once was enough (but read the back as its the most important part). Mosby's tests at the end of each chapter were also very helpful imo. Ask people who graduated for remembered questions as CDCA is notoriously similar, NBDE not so much. With NBDE they have certain topics they want to hit and are going to hit every year (ie. which LA causes methemoglobinemia or some variation of that question, whats the optimate concentration for flouride, etc, etc) . Going through old exams helps you get a feel for the types of questions but don't expect many/any repeats. I'd say the main reason to do a test is becaue you can start to find trends in the type of question they are asking for so some people found that this was helpful. Tuft's pharm review was also super helpful for the pharm aspects. The last bit of it (there was an update at some point and he added a few questions) was very, very heigh yield. Tuft's was a bit overkill imo since pharm was maybe 15-20 questions total but just doing tuft's and skipping mosby's and DD for pharm is totally fine.
My study schedule:
About 1 week total, ripped through the dental decks the first 2-3 days (skipped ortho and pharm) and took breaks by looking at tuft's and then read mosby's from cover to cover for the next 2 days, did one practice exam but was pretty tired so took the last day off. I cram when I study so this might be a bit short for some people but I didn't put in that much effort as I felt pretty comfortable with my clinical knowledge (clinical skills are a big component, what would you do in this situation, what would the treatment be, pathology was a joke because I've seen a lot of the cases, common sense, etc). IMO, much easier test than part 1.
As for decks, not sure. This year is a 'reformulated year' for nbde so the questions change a bit and the fail rate doubles for the specific year (this happens every reformulation year) but I bit the bullet and bought the newest 2016-17 decks. I think it was a bit of a waste but I figured $100 bucks extra for the newest decks would be worth it if I maybe got 15-20 questions right I wouldnt have normally gotten (might be the difference between a pass and a fail). Now I have nothing to do with them but I passed so I guess theres that.
Overall subject break down:
Ortho: barely any questions, very simple. My ortho is pretty weak and I felt fine.
Pedo: Questions regarding behavior and behavior management (modeling, logic based questions like what is the child experiencing, flouride doses, etc)
Path: I didn't think this was very challenging because I've seen a lot of these in clinic so I'm familiar with it. I feel like it would be good to go over path but its not super high yield because they dont ask too many questions. Don't stress about memorizing all of the tiny details of every disease out there. You're going to need to know dental stuff like amelogenesis/dentinogenesis imperfecta (Either details about it, or ID it or how would you treat) but for the more uncommon pathology generally you can exclude half the options because they just dont make any logical sense (radioopacity shown, it definitely isn't ameloblastoma, you know?) so you're guessing 50/50 on the harder ones if you don't know them.
Perio: I didn't find this difficult but other people mentioned theirs drilled perio pretty intensely. I felt it was pretty logical (a lot of questions asking the same thing, try to do SCRP before you do surgery...calculus causes everything)
OP: No need to memorize specific dimensions or inlays/onlays or gold. I should have skipped this part of mosby's tbh. I found it pretty basic, just know when to use composites and when not to. A lot of gimmes (i.e. you can't isolate, would you still use composite? of course not).
Endo: Breeze. Know the diagnoses / treatment cold. But a quick run through either the deck's or mosby's would be sufficient. This seemed like the easiest part of the test.
Patient management: Read this part of mosby's twice or three times. A few more difficult questions from this section (know the numbers, know the insurances, know the billing, autoclave stuff, etc). I'd say this was the most 'memorize' aspect of the test other than pharm.
Prostho: Review if you aren't familiar with anything but it seemed pretty straight forward. Lots of 'what would you do in this situation, how would you treat' but a most of it was easy so long as you treatment plan while in clinic. If your instructors spoon feed you things in clinic then you might struggle with this section and the OP section but overall it wasn't too bad. You wouldn't do a distal extension cantilever bridge for a molar replacement, long span edentulous area, you'd do an RPD. A couple of questions where there was just no good answer in my opinion (crown a perfectly good tooth, extract a tooth with simple MO decay, etc, etc) but no way to prepare for those.
Overall, I found 60-70% of the test pretty straightforward and clinically relevant. The other 30% was poorly worded, impossible to see clearly, a situation where I thought there were multiple wrong answers and no right one, or simply a good question that I didn't know the answer to. Good luck, hope this helps!