All great questions, MoMosMoProblems. I'll just disclaim this by saying these are just my opinions and outlook on Sporcle-related topics... others should chip in too to offer their perspective.
1) As you know, there are fifteen sections we call 'categories': Sports, Movies, Science,
etc. If you go to 'Play' at the top and choose a category like '
Geography', on the left-hand side, you'll see a list of subsections, what we term 'subcategories'. Ones in Geography include ones like, 'Asia', 'City', 'Topography',
etc. When you say 'pick one', I'm assuming you mean, how do you assign a quiz you've made to one of those subcategories. The answer is... you're only required to assign your quiz to one of the 15 categories. Then your quiz will show up under one of those 15 categories in the Quiz Lab. And if your quiz gets Editor-picked, it will show up on the category page.
Subcategories work differently in that they're more flexible, and that they are heavily related to your tags. You don't have to assign your quiz to any subcategory/tag, but tagging your quiz properly has its benefits. If you're tagging a quiz on Harry Potter characters, you might tag them under 'Harry Potter' and 'Literary Characters' and maybe 'Young Adult'. The curators for those subcategories who come across your quiz might consider making it a Curator's Pick. The mechanism that allows them to showcase it in their subsection this way is tagging. If their 'Harry Potter' or 'Young Adult' tag is not there, they can't CP it. That's why it's a good idea to choose your tags wisely. (As an aside, though, curators of subcategories can add tags for you. However, it is also part of our duties to encourage quizmakers to add the tags themselves first before taking things into our own hands.)
Regardless of what tags/subcategories you want to associate your quiz with, such a quiz should and would be filed under 'Literature' in the broader sense, for sorting purposes in the Quiz Lab, and outside the Quiz Lab if it ever gets published. There are no 'rules' or restrictions on what subcategories you think your quiz belongs in.
2) When we have a quiz that's cross-category, every quizmaker on here approaches this issue differently. I think most people try to go with the category that has an audience who would enjoy it the most. I agree your quiz on bilingual songs by foreign lyrics, to me, 'feels' more Music. If it was identifying the
language from a set of lyrics, though,
that quiz should go in Language in my opinion. The song titles just tips it over the edge to more the Music side of things. It's the same case for your soundtracks quiz. If it were me, I would think to myself --- would music gurus or movie buffs
know the answers more, and have
more fun playing it. I think movie buffs know soundtracks better than people who are interested generally in music. If you go to the
Music and
Movie category pages, on the left-hand side, you'll see that a quiz on soundtracks do not fit any of the Movie subcategories aside from 'Movie Titles'. Likewise in Music, there's only the 'Song' subcategory. Sometimes there's nothing that can be done about that --- there's just no 'Soundtrack' subcategory. And that's okay. You've found loads of other tags that can kinda be used. That's good anyway, because someone might type those things into the search bar at the top, in search of quizzes on 'movie songs' and 'soundtrack'. They'll find your quiz that way, and not everything has to go through those 'official' subcategory names.
To sum up, if you're not sure about category your quiz belongs in, go with your instinct. If you're still not sure, ask on the forums. Or you can e-mail one of the relevant curators and Editors to ask, or any of our fellow quizmakers who have an e-mail on their profile. Most of us are pretty open to offering others advice. A lot of us do this actively on and outside this forum, concerning a lot of the quizzes we produce. Feedback is always great to get, whether that's before or after you release a quiz. (Another aside, all curators and Editors can check out your quizzes before you release them, via a 'test link'. When you 'Test game' before releasing it, the URL of that page is the 'test link'.) And through this process of talking about quizzes with other users, it's also kinda nice to make new friends, especially ones who're just as nerdy. :)
3) Editors (the 15 of us) all approach our duties differently, but in general, we all work hard to ensure we don't miss any gems out of all the quizzes that get contributed each day. How long it takes for them to check it out depends on the Editor, but we're typically quite on top of everything. You can be sure a user like yourself, who puts in effort to make your quizzes look good, will get our attention --- especially by being open with your doubts and inquiries on this forum as well. Like I said under 2), being active and talking is a wonderful thing.
Some Editors talk more than others. Just because the Editor of your quiz's category didn't leave any feedback doesn't mean they didn't like it, or are going to dismiss it entirely. First and foremost, our job is to highlight good work. Maybe the Editor has a bunch of others lined up for EP's before yours can fit into their schedule. Maybe they don't think it would have wide-scale appeal to their category's audience. Regardless of our personal preferences, and what we find fun, I think we all endeavor to keep the EP's versatile in subject matter and quiz type. We also try to avoid favoritism, and try not to EP the same user too many times in a duration of time. There are plenty of reasons your quiz may not get EP-ed, but it doesn't mean you didn't produce something good. We each have hundreds a month we have to consider.
So, I think the easiest way for you to get answers on these issues is just to contact them privately --- most of us have something on our profiles for you to use to contact us. There's always the chance your quiz may still get the recognition of an Editor. Just remember that even if it doesn't, there may just be other criteria we have to look at.
More in a bit.