If you have never touched Agile before that will be the additional learning you would need to do, the PMP questions are very broad so it doesn't matter your discipline.
The PMP is VERY difficult, it requires a deep comprehensive knowledge of a very broad range of domains and memory recall plays only a very small role in passing the PMP, ( i.e. EVM formulas etc). You cannot cram or think memory will get you through! I just did my PMP exam yesterday (29th July) and it was without "question" the hardest test I have ever done!!
At the first break I was thinking about when would be a good time to sit the test again I was convinced I had failed. It was 4 Hours of some of the most difficult questions I had ever seen and only about 5 to 10% of the question I felt for sure I knew the answers, all the rest I had doubts and was really worried I would fail every domain badly. I left the exam convinced I had failed, I felt broken and numb.
When you do it online it can take up to 5 days to get the results, but PMI was on the ball and I got the results back in 24 hrs, I PASSED and got all 3 domains above target! But after those 4 hours I was a total wreck, drained of all energy and I have still not recovered today. Its mentally exhausting! Even if the online process was smooth with no issues, I did a lot of prep ensuing the room was "clean" , also you need to keep you face always in the camera which just adds to the stress. An overall very stressful experience, but with a great goal at the end of it! Also I have no issues with the online process and checks as it ensure the integrity of the exam and the certification!
But the question to ask is not is the PMP difficult to study, but is possible to pass? Being difficult does not mean impossible, many things are difficult but with right commitment most people can do it. But you cannot wing it, you need to really commit to it. There has never been more resources and materials to pass, and many of them free on youtube etc.
But you have got to commit serious time, to give you an example I read PMBOK 7 and Agile practice guide cover to cover at least 3 times most likely 4 to 5 times the PMBOK 6 now called Process group practice guide. I then did at least 1500 questions, then 2 mock exams on prepcast, and then 2 mock exams on PMI Study hall, plus at least a few hundred or so practise question combined on prepcast simulator and PMI Study hall. Of course all this was on top of the 35 PDUs hours which actually took me 50 Hours as I did others tests etc. My target was not just to pass the exam but to become a better PMP and have a deep understanding of the best practises, getting the 3 ATs was just icing on the cake.
Also do not look for PMP Gurus or quick fixes and promises to pass in 20 days etc! Stick with experienced and tried and tested professional training such as Prepcast. You will not hack your way, or cheat code your way through the exam, of course there is a mindset and values but that's not a cheat code, thats an instinct and takes hundreds if not thousands of questions to build up.
When you do the PMP exam you sign to state you will not reveal any of the questions, and I have no intention of breaking that promise, all I will say the questions were hard and I feel almost design in away to stop cheat sheet style approach based on rules, such as if you see "XYZ" in a sentence its the wrong answer, I would say they have doubled down on ensuring its based on comprehension and deep know how. But again put the time in and you will pass it. But its "HARD" But that is why its worth it!!! Not just anyone can get a PMP. In the end I will commend PMI they really have designed a very challenging but also very good test that ensures people who pass have a deep knowledge of the subject area. Getting a PMP really means something, and if you have genuinely met the entry criteria to take the exam, then you can pass it! Buts its difficult for a positive reason as you taking in so much best practises that will make you a much better PM! Good luck and lets us know how your journey goes! I wish you the very best on your path to certification!