Not quite correct. Grin’s Pow since the last hardfork is Cuckatoo32+.
That means that it accepts all of C32, C33, C34, … up to C63.
But of course C32 is the preferred choice since C33+ puts much higher demands on mining hardware and software, and we may never see ASICs supporting C33…
There are CPU lean miners that will do C33+ but they take more than a minute to process one graph so it’s rather pointless. A GPU can do it in under a minute but it’s almost an order of magnitude less efficient as there will be few sequential accesses to RAM.
The best hope is a slean GPU miner which @Lolliedieb has written (not sure if it’s part of the publicly available lolminer) which I believe would be within 2x of the efficiency of C32.