Shrinking the database partition if autogrow is turned off?
You can shrink a database regardless of autogrow setting. These are unrelated except for the fact that if autogrow is off, and you shrink the database, you're likely headed for a failure as soon as you start adding more data. This obsession with shrinking files is unhealthy - why are you going to shrink the file? What are you going to do with the space you freed up, but only until the file has to grow again? If you are never going to update the data that's there or add more data, maybe this strategy makes sense, but for an active database, it just doesn't accomplish anything except cause you more pain (maybe not today, but it will catch up to you).

No, seek times are not increased because a file is large. The file is just a container.