Creativity? Mac Required?

Let's start with the second question first: "Should you get a Mac?"...

Do you need a Mac to be a web developer? No, there are plenty of devs out there who still rock Windows however I will say that a lot of the tools out right now for web dev were built for Bash and are generally easier to get up and running with. I worked between Windows and OSX for a while and setting up tools like Node on Windows was simply a nightmare. Most agencies are using Macs, so you'll most likely end up having to use one.

To sum up that answer, you don't need one, but it will help you out in the long run if you can afford it. I'd highly recommend getting a Mac. Don't feel like you need to have one though, save up if you want one.

For the other kind of question about creativity...

There are a lot of job postings where they mention handling design, but in reality many of those posts are written by non-technical HR people and are generally nice extras instead of requirements. Some places are looking for someone who can do a bit of both, but generally you will often find most places have dedicated designers and creative directors who will take care of the design.

What you really want to be concerned about from a design standpoint is handling responsive design changes as the layout changes. At places I have worked at, I've only been given at most two design layouts, mobile and desktop. Sometimes I have gotten only the desktop layout. You'll generally be expected to fill in the blanks, and adjust design elements so they look correct at all viewport/device sizes.

Depending on the job, and this will take the proper round of questions to determine if it is right for you, you won't typically be the person doing the "creative" work. You just need to speak to the interaction part of design (sometimes) and the occasional solution for various layouts on different devices.

With all that being said, you should take some time to learn the basic principals of design. Color theory, gestalt theory, usability, proportions, layout, concepts like the golden ratio and two-thirds rule can go a really long way. If you are just starting off, hopefully you'll find a job where you work in collaboration with a team and can be mentored. That is when design really clicked for me, I worked for a great creative director who taught me a lot of the design fundamentals I use on a daily basis.

Windows will have the bash from Linux within an update in the summer 2016. And it will be a native to the OS so it's not a fired up from a JVM.