I’d second this. I’m on linux, so ymmv but 7640u is pretty good with basic work. I’ve also written my own software to limit processor power usage to prevent ramp ups / save battery when on heavy loads, so I pretty much have a silent laptop.
The caveat is that I haven’t tried the 125H. My previous laptop was the 12th gen Intel FW13. That one was a little too much. I even changed the thermal paste to the PTM phase change one just to get some better thermals and reduce the ramp up.
I reckon the 7640u will be slightly lower in general, but i don’t think you will be that far off either way.
Your main challenge will be preventing the ramp ups during heavy load (an issue for both intel and amd). For that you’ll need custom software. I’d recommend using the framework hub if you’re on Windows to control this.