They definitely specify your pitch/roll level with the horizon. The cruise attitude question is a little more complicated. My understanding is that in FBWA, with no pitch or roll inputs and a cruise throttle setting, the autopilot is attempting to keep the pitch and roll atttidue of the airplane at zero and zero according to whatever is set with the AHRS_TRIM parameters. Stabilize and hover (altitude hold mode in copter) basically work the same way. However, in my experimentation, I've found that the AHRS_TRIM parameters have much less effect in AUTO. Without an airspeed sensor, the biggest single influence on cruise speed that I've found is the physical pitch trim (i.e. the amount of up elevator and/or stabilizer incidence) when your pitch servo is at its trim value. I was able to change the cruise speed of one of my airplanes by +5 m/s (that's almost 50% of the max endurance speed) by simply decreasing the trim angle of the full-flying stabilator by a couple of degrees, with no changes to the autopilot I've also had an autopilot fall off its mount during flight so the HUD was showing ~20 degrees of bank and ~15 degrees of pitch in level flight, and it continued to fly fine in AUTO mode.
The reason why I asked about different AHRS_TRIM values for vertical and forward flight is that I found the AHRS_TRIM values I set for what looked like an appropriate amount of nose-up pitch for forward flight causes my tailsitter to constantly drift backwards in a hover. With two separate trim values, I can set up my Q trims for a stable hover in no wind, and my forward flight trims for the most efficient cruise attitude in forward flight.