What is the best job for fresh graduates to improve chance of being admitted to top grad programs? I have just obtained my B.Eng degree and I intend to pursuit a career in academia. However I decided not to immediately go to grad school in the USA.

During this time, I am considering among different working options to improve my graduate profile to top grad programs. Please help me evaluate between these 3 options, and clarify my doubts in each option. Besides, which is the most common option, for someone who does not want to immediately study PhD right after bachelor's?


To work in industry, while continuing doing research with my mentor in my free time. Then I would apply for grad schools this autumn. With this option, I will have more industrial experience but less time to finish my journal article and for research. My question is I'm not sure if the above industrial position would help my PhD admissions in any positive way. Keep in mind that the job is not related to my research interests but the skills I learn might be helpful for grad studies (programming skills in other languages, for example).
To work full-time as a teaching and research assistant (RTA) in my undergrad university. Then I would apply for grad schools this autumn. With this option, I will spend most time doing research, which I enjoy a lot, have more time to finish my journal article, and even have a chance to write more papers. However, it's unlikely that the status of my future pubs would be "published", or even "accepted", by the grad admissions deadline (December this year). Another thing I'm wondering is, is RTA considered a serious and legitimate "job" in the USA? Does it negatively affect my grad admission in any possible way? For example, the admission committee might think that I am not mature enough to pursuit a "real" job after graduation? By the way, this RTA position I'm aiming for is full-time.
To attend a MS program at a prestigious university in Europe or Asia. Then I would apply for PhD in the US after its 2-year program. With this option, I can have a degree from a more famous institution, considering the fact that my undergrad institution is not well-known internationally. I think that a degree from a repute university would be a boost to my application. Am I right? Even if I am right, is it worth my time? However, I realized there are many drawbacks to this route: potentially not over-the-top master GPA due to the rigor of the program, much less time or even no time for research due to heavy coursework. Even worse, I came to know that US grad schools often do not value master degree from other countries, which mean I would very likely have to repeat many coursework if I am accepted to a US PhD program.


Some size notes: 


My field is engineering, however, I gladly welcome answers from people with different fields.
My current mentor has some very good contacts in top US grad programs. This make the purpose of Option 3 less appealing.
The best job option is the research assistant or research and development related position because mentors or advisors want to see you are capable of doing independent work and that you are familiar with publish or perish practices in academia.