Having extra research stations speeds up research.  However, in my experience, most games are over long before that would make a difference, simply because much of the research can be skipped.  For example, with the logarithmic function limiting income, it can take a really long time to repay the investment into "immense cargo holds".  If you think the game isn't going to last forever, skip it.

Yes it does, but not much.  I was curious enough to edit the files and make them free, and use fewer slots.  If you have 100+ of them, you can trim total research for everything down from about 5 hour to 3.5 hours.  So.... not worth it.