There is a huge variety in the quality of writing in scientific papers, but most of it is bad, or at least totally opaque, so I'm not sure that 3 papers will gi

There is a huge variety in the quality of writing in scientific papers, but most of it is bad, or at least totally opaque, so I'm not sure that 3 papers will give you a sense of what is good, or even have a high probability of containing a paper that you can use as an entry point, although I think your premise is correct. Probably the best evidence that a paper is a good entry point is whether or not the author cared about the abstract. A lot of scientists treat it as a chore, picking some key points from the premise, methodology, and conclusion sections, and haphazardly pasting them together into a miniature version of the paper. An abstract is a sketch of your argument. It's supposed to be how the author thinks about the work they are doing, in terms of how it relates to the work everyone else is doing. Look for an abstract which presents an argument in plain english and isn't afraid to give a little background or motivation. It might take dozens to find one though.