Regarding the question about whether all airports use traffic patterns (These comments apply only to the USA. Regulations may be different in other countries):
On airports with ATC (control tower) the controllers will instruct you on what kind of a VFR approach to fly. Most airports handle light and slow general avaiation aircraft differntly than they handle heavy or fast aircraft. On most airports, fast or heavy aircraft will be vectored so they can fly a long, straight-in approach to landing. They will be iniatially positioned on a course line leading to the runway anywhere from ten to fifty miles away and then will fly straight to the runway. At the same time, light aircraft will either be fed into that straight-in approach closer to the airport or will fly a traffic pattern, possibly to a different runway.
For instance, using your runway 80, you may receive instructions similar to "Cross mid-field at or above 1,000 feet, fly left traffic to runway 80, cleared to land". On your own navigation, you are then expected to fly to the airport, maintaining the designated altitude, cross the center of the airport on a course of 170 (the crosswind leg), turn to a course of 260 (the downwind leg), turn to a course of 350 (the base leg), and, finally, turn to a course of 080 (the final leg) and land. Traffic pattern turns are always 90 degree turns and you are expected to fly wind corrections such that your course over the ground is at the designated direction.
Most IFR approaches are straight-in in the near airport environment. An IFR approach that requires turns close to the airport is called a "circle-to-land" approach. All aircraft, regardless of size or speed fly the published approaches, however, ATC may designate different approaches for dis-similair aircraft, depending on their traffic conditions.
At uncontrolled airports, there a "safety suggestions" published in the Federal Air Regulations" but they are not requirements. Legally, you may fly any type of approach into the airport that you can accomplish safely. The suggestions include flying a pattern appraoch rather than a straight-in but many pilots fly straight-in if there is no conflicting traffic.
These comments apply only to the real world. I do not know if FS designates the type of pattern to fly or if they just clear you to land on a given runway.