Will Cargo ships be able to achieve a higher top speed, but slower acceleration, or will pilots be forced to self destruct to avoid being intercepted by an interdictor?

No. The way they want the game play to be for cargo haulers to an extent is like the navy where your bigger ships are slower and vulnerable, but have escorts. So if you wanted to go into a less secure space, you have a risk versus reward and whether or not you want to pay for the extra escorts.