What is the difference between systems engineering and information technology?
First of all, I don't think the specificity of your degree is relevant to your start-up, unless you have a very specific business model in mind. Even that will most probably change though even throughout your studies. Your question implies that you have already a first degree and that it is in a different area from the subjects you mentioned, otherwise you would have some idea about them. As another answer mentioned, "information technology" can be perceived as a subset of "systems engineering" (especially software engineering). I can't really help you with systems engineering, as I come from an IT background myself. I think your choice has to do with your interests and inclinations rather than your career path, especially if you want to start a company. And I don't know how relevant a systems engineering degree would be in a start-up context (also already mentioned). If your interests lie for example in software, for example creating a SaaS start-up, then you should look towards IT (regarding the options you mentioned). If, however, you want to do something that involves assembly lines then look towards system engineering. But since you are aiming for a start-up, maybe you'd better decide on your product first and then direct your studies accordingly.
What is the difference between a strategic information system and a srtategic level system?
They both are pretty much the same. Main difference is the info system takes in more detail.
Difference between Information technology and Computer Science?
I also used to be confused about exactly what the difference was between Computer Science and Information Technology, but eventually figured it out as time went by. Here's my breakdown of each: Information technology(IT) discusses how to properly use computers within a organization in order to help solve business problems and meet their needs. An IT degree program at a College or University will teach you how to develop and use computer applications to share, store, and manage data and/ or information. Topics you might discuss include database systems, programming, networking and telecommunications, information security and assurance, web development, human computer interaction, etc. IT degree programs might also require you to take some business or management courses as well. Computer Science(CS) is using theory and science in order to create and build usable applications, like video games, iPhone apps, computer programs, etc. A CS program at a College or University will focus more on the theoretical and mathematical aspects of computing. Topics may include software development and design, algorithm analysis, data structures, computational theory, object-oriented and systems programming, computer architecture, etc. Most CS degree programs include quite a few sequential math courses such as Calculus 2 and 3, as well as more upper level programming. To keep it simple, Computer science is more about the developmental side of computers while Information technology is concerned with the business side of computers technologies. Hope this helps and best of luck to you. Please check out my link below for more info