The chip reportedly has a single-precision floating point performance of 5.5 teraflops. For comparison, a full Hawaii/Grenada chip has 5.2 teraflops on its specification sheet so on paper the performance-class Polaris doesn't seem to be much faster than its predecessor.
The main metric where it promises to score a lot better will be performance/Watt. Polaris 10 reportedly has a TDP no higher than 150W, significantly less than the 250W TDP of the Hawaii-based chips. This also means AMD could use just one 8-pin PCIe power connector, just like NVIDIA does on the GTX 1080. TechPowerUp writes Polaris 10 has a 256-bit GDDR5/GDDR5X memory interface, 8GB could be the standard memory amount and the first SKUs could feature 7Gbps GDDR5 memory.
Polaris 11 (aka Baffin) will be the new mainstream chip and TPU heard it could feature 14 compute units, which would work out to a stream processor count of 896. You can expect a 128-bit GDDR5 memory bus with 4GB memory, a TDP of 50W and single-precision floating-point performance of up to 2.5 teraflops. This GPU is a replacement for the Tobago chip.