I can’t give you a figure for the 12th gen Framework, but Linus Tech Tips has done videos on this before testing the difference, and it can amount to 10-15% depending on how memory-intensive the task at hand is.
You might be interested in these benchmarks. While it’s AMD (threadripper) and linux, there is quite a bit of benchmarks, so you will probably able to determine if it will impact your use case significantly.
Just wondering. I am trying to get one of the Alder Lake N series mainboards with soldered LPDDR5, probably the i3-N305 or maybe the N200. Maybe seeing how small those mainboards are, probably see if I can fit it within the chassis for a very low power system. Those only have single channel memory, so I wanted to gauge how bad would it be before attempting it.
I did consider getting a RK3588 baseboard and find a hacky way to do it but the price/performance was kinda bad.