If the results are not consistent, that's probably caused by either backlash of friction in your printer mechanics, or the bltouch not producing consistent results. What probing speed are you using (F parameter in the M558 command); and are you probing with the bed heater off or on?

Yes, that will work. The G32 command is needed only if you are using multiple independently-driven leadscrews for the Z axis and have used M671 to set up the coordinates; then G32 will probe the bed and adjust them to level it. If instead you have a single Z motor and a belt driving multiple leadscrews, then you don't need the G32. If you have a very accurate and level build, you don't need G29 either. The bed compensation figures in the M122 report have no meaning when mesh bed compensation is in use.