To deal with the collisions between staves when importing MIDI files with many tracks, I suggest you go to the Page Layout page of Layout Options and set the page size to A3, and perhaps consider reducing the rastral size a bit, too.
When you import a MIDI file, quite often you may find that you need to change some of the instruments in order to make a “real” ensemble that makes sense. This is why we provide an option when importing MIDI files to import all of the tracks into a single player group, which you can then have alongside your real destination instruments. Copy and paste the material from the imported tracks to the real instruments, then finally delete the player group containing all of the players created for MIDI import. You should do this in galley view so that you can workably see two ensembles at the same time. Another approach is to have two flows in your project, one with the MIDI players and the other with the real players, and use two layouts, one showing the imported MIDI flow and the other showing the empty flow, and open two windows on the project so you can copy and paste between the two.