The PowerPrep provides the exact interface you will receive on the real GRE. So try a practice test on PowerPrep II.
Other than that ther are absolutely no format options available. You are given a text box to type and are not allowed to change anything (font, size, spacing etc.)
As for the topics, there are no common topics. It's just random. If you have enough time just look at all the topics and try to come up with sort of outline (your opinion, examples etc) for each topic. This way you will know "what to write" on any topic you are presented during the test and you can be able to save time as well. Hope this helps.
And do the PowerPrep II practice tests!!