Titles and descriptions can get blurred very easily. And even more so as people and companies scramble for jobs and business.
"Engineer" once pretty much meant something physical was involved. "Systems" meant more of a design/planning view of things.
And I am more than willing to concede that there can be a widespread discussion of associated meanings and definitions. Not going to resolve that herein.
To your question: only you can decide. Start by looking at employment ads. See what titles are being used, read the job descriptions, learn the terminologies, acronyms, phrasing, job/position descriptions, etc..
Google what you find and wonder about.
For the most part many job descriptions are very broad and list any number of educational, experience, and skill requirements.
Reason being is that most IT folks end up doing many different things at any given time. And positions for government contracts often require (rightly or wrongly) some specific "buzzwords". And by presenting broad requirements the potential employer has more freedom to select employees with less chance of some discrimination claim.
Employers will hire you if they decide that you can do the job and be a "good" employee. Period.
What those disciplines are "about" is the question. Learn but remember to keep yourself in the loop. What are you "about".
Keep yourself balanced between the two "abouts". Will not always be easy nor always work out per se.
Do what you like/love. And that is likely to change - go with the change as well.
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