> The Tom's review of the revised Crucial P2 500GB was a 2-chip and the QN322 2TB also appears to be 2-chip vs 1-chip for smaller capacities of the QN322, so the performance boost from higher capacity won't be there.

You need to make the distinction between how many packages of NAND flash are soldered to the PCB, and how many dies of NAND are stacked in one BGA package. A 2TB SSD requires more than two NAND dies because the largest NAND dies in production are in the ballpark of 1-1.33Tbit, so a 2TByte drive would typically have 16 NAND dies in total.

> And the SLC cache size isn't fixed but rather a fraction of the free space.

That doesn't stop a 2TB drive from generally having 4x more SLC cache than a 500GB drive, other things being equal.