I use RX580 Nitro+, and get 24 MHs only.
On the boot screen I see:
GPU[0] : Supported GPU Memory clock frequencies on GPU0
GPU[0] : 0: 300Mhz *
GPU[0] : 1: 1000Mhz
GPU[0] : 2: 1750Mhz
GPU[0] :
Where is 2000Mhz and more?
If you know the GPU supports those clock settings; it is probably a driver problem; After stabilizing the nvOC update I will make a new rxOC version ( it is overdue ).