What's the impact of former university's transcript on PhD application?
Every field (chemistry vs. mathematics vs. history) is different and every PhD program at different universities you apply to is different. Also, who serves on the PhD admissions committee may change year-to-year.

Yes, many top-tier programs will look at your GPA. How much weight will they use to judge your application is variable. I can imagine a situation where the five professors on this years admission committee decide to stress class grades for incoming students.

Yes, many program will seriously consider any research you do, even if you never published anything. Simple being involved in an processor's research laboratory will most likely give you an advantage. I can imagine a situation where the five professors on next years admission committee decide to stress undergraduate research in incoming students.

My point is the following: You can't predict what will get you into a PhD program because it may change year-to-year. 

What I would do: It would be nice to find a way as an undergrad to research something, but I wouldn't stress about it being publicly published. It may be enough to have a strong undergraduate thesis, similar to a senior-project, that shows your research ability. That with a good recommendation letter from one (or more) professors you work with will be the building blocks of a strong application.