According to the firmware data from AMD, N21 has 80 CUs which would be 5120 "shader cores".
https://twitter.com/_rogame/status/1289239501647171584
The amount of ROPs is even, 4 Render Backends per Shader-Engine, so either 64 or 128 ROPs.
It's likely that AMD changed the amount of ROPs per RB and is going with 128 ROPs.
I drew N21 with 2048-Bit HBM2(e), which fits to the amount of L2$ tiles (16 texture channel caches for 16 memory channels).
(On a side note, Arcturus doesn't make a lot of sense with 16)
Otherwise it would be a 256-Bit GDDR6-Interface, where rumours from RedGamingTech have it that "128MB Infinity Cache" would balance it out, which I'm not inclined to believe.