You can't compare Vega to RDNA2. Especially when there is an 18% die shrink involved.Rembrandt's iGPU too wide to just be designed around the laptop market alone. Based off my 6700XT testing, I see absolutely no reason for AMD to go with 12CUs for mobile alone, as in the same 25W power budget for the GPU CUs alone, you could instead go with 8CUs (-33%) clocked 300MHz higher (+15%). At lower iGPU only power (AKA in more CPU heavy games or lower power budgets), this gap would measurably shrink.
Especially not as the iGPU will likely be enough to beat Intel ones out to 2023 or perhaps even later if MTL and LNL do actually come with Gen12 as previously rumoured.
Large APUs on the desktop are pretty much going to be necessary going forwards, as taping out small dGPUs becomes less and less cost cost effective going onwards from here.
Without doing something awfully strange like backporting new IP to 12LP+ or something that is.