You should almost always limit questions to a single universe
(Since you've posted your question about both Star Wars and Star Trek I can explain in general terms as well as give specific reasons why questions should generally be limited to a single universe.)
The help center's guidance on tags is relevant here since each universe usually has its own tag. One of the main uses of tags is:
Tags are a means of connecting experts with questions they will be able to answer by sorting questions into specific, well-defined categories.
This use of tags tends to break down if you ask a single question about multiple universes. For example, what if I'm an expert for one universe but not the other? That's exactly the case for me regarding the question you asked -- I'm an expert in Star Wars but not Star Trek. If I know the answer to the Star Wars side of your combined question I can't really answer your question because it would only be a half-answer. That's not a problem if you asked two separate questions, though -- I could answer the Star Wars one and let a Star Trek expert answer the Star Trek one. While there are some users who are experts in multiple universes (e.g. @Valorum, an expert in both Star Wars and Star Trek), these users are rare.
Tags are also used to
help you identify questions that are interesting or relevant to you.
What if I'm interested in one of the universes but not the other? If you post a combined question about two universes then I've got to extract the information about the universe I care about from the "noise" regarding the universe I don't.
The exception to limiting a question to a single universe is when you are asking for a comparison between two universes using objective criteria.1 For example, Which ship can go faster, the Millennium Falcon or the USS Enterprise? can be answered using objective criteria because each universe provides information on the ships' speed which can be converted to common units: the speed of light and a light year.2
Your question, however, asks about the capabilities/limitations of the two technologies which are fundamentally different: Star Wars' hyperdrive vs. Star Trek's warp drive. There's no benefit to combining a question about the minimum distance required by a Star Wars hyperdrive and a Star Trek warp drive because you're specifically not asking for a comparison between those minimum distances, just what those distances are.
You seem to want to combine the two questions to reduce the number of questions you have to post. But there's no limit on the number of questions you can ask, so you might as well post two. The answers to each universe are totally separate so you don't save the answerers any work by posting one question, either.
1Otherwise, the question falls into the "Gorilla vs. Shark" problem.
2Fortunately, we do not have to rely on the Star Wars definition of a parsec.