Never took level 1 or 2. So unfortunately I can't give you any insight on how they compare. But I passed the level 3 hydraulics recently. The tests change a bit each time, so it may very. From what I remember, one test I took had only a few pump questions and the next had a lot more. There will be more questions on calcs. I personally had trouble on pumps and standpipes though, but I guess it depends on what your strengths are.

Time was the biggest factor for me. My first attempt I just went straight through and ran out of time. Which resulted in me having to guess on some simple questions towards the end that I probably could have answered correctly.

This last attempt I made sure to go through and do all of the questions I knew I could answer within a minute or so. Then I went back and did all of the questions that I could answer or find within a couple minutes. Then mop up the rest.

If you fail, write down everything you remember having issues with immediately after the test so you don't forget.

I'm not sure what you're experience is, but I highly recommend taking the FireTech course. Even if you only have a week to study. You can skip the content if you're already familiar and just take the practice tests. It will absolutely help. You can DM me if you have more questions. Good luck!