I believe it prioritizes results from the current area you’re in (though I’m not certain this is consistently done). You can also limit the results to a particular section through the three dots menu or query modifiers like in: files. There’s always room for improvement though.
I haven’t noticed it being too small, but there are other factors that influence that like my own browser settings and maybe I don’t use it heavily enough.
Adjusting sorting does like it could be a nice addition. I’m not familiar with this area of code, but poking around just enough to potentially say something that is completely incorrect… It appears the search code already exists for handling ordering by date, size, etc. in the backend. That would be good news if someone find the desire to pick up the frontend pieces.
Depending on your needs, there is also the fulltextsearch app (and associated add-ons).
Actually you’re in luck: there is current work right now on this:
There are also some existing enhancement requests (some of which overlap either with the above or with each other), which you might want to put your vote in on by adding a to those important to you: