Well, most active and passive basses when you don't use EQ are very similar. After all, the front end of your head is basically an active preamp! An active bass merely moves part of that EQ circuit into the bass where it more convenient to adjust while you are playing.
In the Common Application, it says that the Personal Essay should be at least 250 words, and attached on a separate sheet (presumably, if you're submitting it online, you attach a one-page file).
How are the GRE essays different from the essays I wrote in school? Unlike many essays you write in school, you'll only have 30 minutes, and you won't be able to use reference materials. Graders won't be expecting perfection; they will be judging your GRE essay for what it is: a first draft.