I believe you do not have to land just orbit the asteroid for this to work in game (In Aurora I do not believe space ships ever land on planets). As for the window of relative speeds I do not know of a widow with that feature.
You can select a fleet, then navigate to or select the body and order to your fleet to “Move to Location”: the ships remain in orbit around that body until you move them to somewhere else, so it has the same effect than landing on it.
As LordPC said, in Aurora, ships never land on a body. Ony fighters can do (at least, it is true for versions up to 2.7.1; with 3.0.0, we will see if also ships up to 1,000 tons could do).
For the second question: the window “System Generation and Display” contains all the orbital data about all the bodies in a system, but respect to the primary (or respect the star the body is orbiting, in binary or more stars systems). This window can be opened by the icon named “Open System View Window”.
Also note sometimes when one release tractored ships at a body the released ships are not actually in orbit but instead the new fleet cab be at the spacial coordinate near where the body is and when this occurs the new fleet needs a 2nd command to orbit the body.