> want it to help with the latency

Primarily the bottleneck actually. PCIe bandwidth is extremely limited.

GDDR has worse latency than DDR and scaling it up to larger capacities faces challenges. So if you unify memory your options are small GDDR, large DDR, or expensive HBM.

Unusually, the BC-250 and PS5 both use GDDR with the CPU so the memory bandwidth is great but the latency not so much AFAIK. It's like using a dGPU as a full computer.