The link give information for complementary and ins13.
Basic (Complementary) : Complementary filter, Gyro, accel + baro / Airspeed if any
Complementary+Mag: Same as above + Mag
Complementary+Mag+GPSOutdoor: Same as above +GPS
INS13Indoor: INS13 with fake GPS
GPS Navigation (INS13): Full INS13
GPS Navigation (INS13+CF): Same as above but uses 2D Mag
Testing (INS Indoor+CF): Same as above but fake GPS
Acro (No Sensors) << Next only, Complementary with Gyro+Accel (No baro/airspeed at all)
Preferred fusion algorithm for navigation starts with "GPS Navigation...."
Complementary+Mag+GPSOutdoor can be used alternatively, only starting with current Next build...
Complementary+Mag+GPSOutdoor is not recommended for fixed-wing because does circles for positionHold. (read Wiki page about circles and CF)
If you don't need extended Nav features, just choose the first (default) "Basic (Complementary)"