You can get by with just leaving it on 10, however your cast distance will be decreased. When you get more experienced with using your thumb as a brake, you can start to back off of the magnetic brake in small increments and adjust it according to wind and cast style. Higher brake setting is recommended for flipping or pitching. The higher end Abu's (Orra and Revo's) have a centrifugal brake system that takes care of the backlash issue when the spool is spinning at it's fastest RPM (beginning of a cast). The higher end Revo (the SX, STX and Premiere models)combine both a centrifugal and magent brake system which almost completely eliminates backlashing.
I personally have the Orra SX and LOVE it! I have no issues with backlashing, however I do have extensive experience with baitcasters and have my thumb very well trained.