Best FW13 config for battery life?

I have a similar question to the OP, except I’d like to specify I’d be willing to tinker (i.e. undervolt, minimal linux install (probably nixOS but maybe debian)) if possible to achieve the best possible battery life. I was initially leaning towards intel, but after reading this post I’m less sure. I suppose I could buy a 7040u and upgrade the battery and camera, but I’m not sure. Just to be clear, I’m split between the Ultra 5 125H and the 7640u. Or if the ryzen ai 340 is better than the other I could spring for that instead.