The impact on performance is more along the lines of 1-2% on AMD (though it likely varies by generation (I did extensive benchmarking on Renoir wrt throughput/latency/gpu). But yes small enough to be insignificant unless you run LLMs or game on the iGPU. I imagine that it also uses marginally more power.

AMD also has a second encryption mode where the OS decides what gets transparently encrypted, it doesn't have to be everything. But that mode is poorly documented (or at least the documentation isn't accessible to peasants like me)