Generally the GPU vs CPU gap on the evaluation side isn't nearly as big as in training. In theory the gap should remain large, but in practice things like the inability to have data ready for batch evaluation means it is harder to saturate the GPU (which as you note is important).

But I'm not sure how much of this applies to chess engines. I see some comments noting that the search part makes it hard to generate batches, but I'm not an expert in this.