need to know from experts, are the concepts tested in the archive still relevant to the actual GMAT?
i.e. are the same concepts tested?

I tried a few and found them to be extremely good and the explanations extremely exhaustive, but i was wondering if d difficulty level is too high for the GMAT?
or is it a good exercise for those aiming a 750+.

i am currently scoring 48 on MGMAT CATs and 50 on GMAT prep CATs.
my test day is 16 days away.

Cheers,
pd