Tal Celest passed the Academy.
Had the same training and experience as Harry Kim.
Is she on equal standing as an Ensign on the Enterprise?
I have no idea who Tal Celest is, but if she was an ensign then, yes, she would have equal standing as an ensign on the Enterprise. Maybe an enterprise ensign would have had a bit more prestige, maybe theyd actually be better at the job. However, they are both of the same rank and would be expected to perform the same duties competantly.
Who else but her, Harry and Seven did they ever show build something?
I recall O'Brian needing ALLOT of help getting DS9 to stay up and running. Sisko built the Defiant, that also trumps O'Brians skills and I also recall Dax having skills in Engineering too. LaForge often asked Data for help for almost EVERYTHING he did. Westly had ideas and created stuff LaForge never even dreamed of.
The difference with O'Brien and Laforge is that they were always the centre of the engineering department, and everything worked through them. Laforge asked Data for input, but it never felt like Data took over control, they always just collaborated. As for Wesley, that was a mistake that the writers got rid of.
I dont think Sisko built the Defiant, and remember that episode where O'Brien was off doing something else and the whole station was suffering. O'Brien was always on a tight schedule and you could see his was pretty vital. Torres never seemed like the centre of engineering in that way, often characters just took over from her.
Since we're not going to agree on this though, I will amend my former statement. How about this: the characters on Voyager, generally, were people first and job decriptions second, whereas previously this was reversed.
Before, most characters started off as either 'the engineer' or 'the doctor', and then their characters grew from that. On Voyager, it seems like the actual characters were worked out before they were placed in their roles on the ship. So, the fact that Torres is a half Klingon maquis is much more important than the fact she is the head of engineering.