The bottom line is that you must do what you enjoy and have a stake in. Popularity in itself is not rewarding. It may even cause you to not be very good if you choose what's most common. This is unfair to your clients, and to others in the field you follow.
Since I've begun Front End Development I've grown more akin to a Full Stack Developer, however I don't say that because the term is daunting with no scope. I picked up mysql, php to allow my sites more functionality, building flat empty pages with no underlying life only interested me for so long. In the end through refining my process & interests I come to a point where I find relation to the Information Architect job title, which is still new and yet to be completely defined.
I began building the aesthetics & functionality of sites, learned databases & server scripting to build site templates & deeper logic, then moved on to refining my practices & coding methodologies. I reached deeper and broader in my own way. You can certainly employ UI and UX as a developer, there is no trade-off. You will be directly involved in building the UI and shaping your UX if anything. Try not to think of specialities in this way. It's rare that for instance, you'll land a job purely because you label yourself as a UI or UX person. You gain the skills by doing the work, and that is what determines your title, your skills, and your qualifications. Do what interest you, pursue & work for it, and it most likely will pay off.
The catch? The catch is not to assume it will turn out precisely as you imagine it.
Glad you picked up the course and it's helping. They will only take you so far, but make for a great initial spike in learning.