As said above,
it is a motivational paper. You will need to learn this information later on anyway so if you consider yourself motivated enough to start the training because it is a job you would like to do I would say you could never study it too much. On the other hand the cubes and diagramming stuff is a thing you either are able to do or you're not. Yes it can help you to do a few just so you get the hang of it on how you have to solve these questions, but I don't feel it will help you to keep on practising on these things over and over again.
On the other hand the documentation is only giving you a very rough information and the statistics are only a guide line, not fixed values.
I would say, for the statistics, make sure you know how different acft's compare to each other (speeds, altitude etc), what kind of acft you can expect for certain flight routes (with regard to distance, size etc).
In either way, you can never be motivated enough but as well make sure your motivating doesn't kill you on stressing yourself out on focussing too much on a certain thing.
Good luck