Yes, the more precise you are in your search (by selecting more filters, like certain libraries), the lower the matching % on the found files will be. This is logical, since the tap2find algorithm in that scenario has fewer files to search amongst.
You are correct in your statement that kick and snare are more important than other instruments on the drum kit. If you want to find something where it’s important that, for example, the hi-hat plays a certain style – just tap in the hi-hat and the files will be sorted according to that. Since you can copy that hi-hat grove and paste on any kick/snare pattern on the song track we figured that this is a pretty flexible (and still easy to use) solution. You can also use filters to further narrow down your search, for example – select the Straight filter, and all other types of MIDI files won’t be shown.
But as all other feature requests you guys have – we will note your request to manually enter which instruments that should be marked as more important in the search 
Henrik Ekblom - User Experience Designer
Toontrack
Thanks for your ideas! We will look at this and see if there’s something we can do about it 
Regarding your question – the limit is not 80% – it’s often the top results are from 80% and up, but as you said, as you filter the results get lower %. The limit is actually a fixed number of results that will be shown (due to technical reasons). But as I said – we’ll look into it!
Henrik Ekblom - User Experience Designer
Toontrack