How do some PhD students get 10+ papers? Is that what I need for landing good faculty position? I've been looking up some PhD students' websites, and there are people who somehow got 10~30+ total papers with 5~10+ first author papers. Many such students are in computer science, but there are a few in fields like bioinformatics. Some garnered 100+ citations before graduation.

How did they do this? This makes me uneasy about my chances for a tenure track position in the future. I just finished my 3rd PhD year at a decent US institution. My field is closely related to bioinformatics, and I am aiming for a tenure track position in a similar field. But if my top competitors are of such caliber (10+ papers 100+ citations), I'm guessing my chances are slim.
I think at least part of the answer lies in different cultures across fields. I did my PhD in computer science/artificial intelligence. There a huge focus is on conference papers which tend to be smaller contributions. Often incremental progress on a single project is reported in multiple conference papers and it was expected that a paper corresponds to several months worth of work. Frequently you would publish in a conference and then have an extended version appear in a journal. All in all, 5 first-author papers upon PhD was not exceptional. Also we had a lot of within-group collaboration so I got to e.g. run a few statistical routines on someone else's data, help write the manuscript and become a coauthor for about a week of work. I ended my PhD with 23 publications, 8 of which were first-author - this was above average in my group, but not exceptional.

Now I do bioinformatics and collaborate a lot with biologists. Their papers are usually longer and for any result you need a lot of tedious manual work in the lab. In turn, the papers represent years worth of work. Many people - even brilliant ones - end their PhD with 1-3 first-author publications. I've heard in some areas, publications are even harder to come by. In other words, the number of publications is not a very good proxy for brilliance, especially when you are ignoring quality and comparing across fields.

As for the 100+ citations - my best bet (since you mention bioinformatics) is that this is because the students co-authored some software/tool/protocol that ended up being useful => cited. (tool papers tend to be the most cited ones). This is obviously a success, but once again does not necessarily imply that failing to produce useful tools is a sign of non-brilliance. 

Example: DeSeq2 software for comparing gene expression across samples has > 10 000 citations on Google scholar while the first detection of gravitational waves has just above 6 000 citations on Google Scholar.

Also me and some of my colleagus have landed reasonable jobs with roughly 0 citations (excluding self).