The weights generated by SimBrief will be correct as long as one of the "Just Flight (MSFS)" airframe profiles are selected when generating the flight.
However, the 146 Professional features a custom Fuel and Payload manager within the EFB/tablet, which must be used to import any fuel/payload from SimBrief. It does not support imports via the SimBrief in-game panel, nor any changes to the simulator's default Weight and Balance menu.
Further info on the EFB/Tablet can be found in the 146 Professional EFB manual: https://support.justflight.com/en/support/solutions/articles/17000134438-146-professional-msfs-manuals
Mark - Just Flight