The autopilot controls the dampening system that prevents pilot-induced oscillation. The autopilot master switch should therefore always be on unless there is an autopilot malfunction. Altitude and attitude hold functions are then engaged/disengaged as needed with the pushbutton switches on the autopilot panel. If you switch off the autopilot you will get a general warning indication. In the real Draken the master switch was wire-sealed in the on position.
Switching between Draken and another airplane in flight is not recommended as this could screw up the autopilot settings.
Well, the 35J could not really do that, so neither can this simulation. But you can exceed Mach 1.8 with some effort. Take off with external tanks and climb on afterburner to 10-12 km altitude, then level off and continue on afterburner. Just watch the fuel gauge!
The general warning light will blink if the afterburner fuel valve is closed.
If you follow the checklist when starting the aircraft you should not have a problem, but if you jump into a saved flight or switch airplanes in flight (not recommended) it is easy to overlook the afterburner valve.
Some of the rotational switches in the cockpit (radio dials, weapon selector, etc.) cannot be operated simply by clicking on them, you must place the cursor over the switch and use the mousewheel to rotate the switch. This is intentional and not a bug, but we will probably bring back the possibility to click-select in the next update as it can be confusing.
Draken 5.0 uses 2048×2048 pixel resolution for the main exterior and interior textures. This means that you must enable high resolution textures in the Prepar3D settings, otherwise the exterior and the virtual cockpit will look blurred.