3rd Level Insurance Appeal Advice?

Has anyone here gone through an insurance/BCBS 3rd Level Appeal? Was it fair and what was the process?

Is the 3rd level appeal process where it goes to a 3rd party/federal charge fair and impartial or is it better to file a fair hearing trial? I’m based in MN.

Some background… BCBS denied two prior authorizations. First was rheumatologist ordered testing for a genetic disease and second was neurologist ordered testing for POTS. BCBS called them exploratory and not diagnostic. The POTS testing has already been completed and they claimed a tilt table test should have been done instead of the testing ordered… I told them the testing is all inclusive with the tilt table as one of the tests completed. They said I could appeal and I countered with no thanks, let’s go to a fair trial. Management offered a 3rd level appeal instead but that seems like it could be a trap.

Btw, POTS was confirmed along with some other dysautonomia.