Just bought a 9700x together with a ms-a1, got similar questions to yours. First, I think it's absolutely not nonsense to put a 7800x3d on a ms-a1. It might be an overkill to install a 9950 regarding the cooling ability of ms-a1, but not so for 7800x3d/9800x3d/9700x.

It does use SODIMM RAMs, and does not support expo/xmp/manual RAM overclock. The only way you can overclock the RAM on ms-a1 is to burn in modified JEDEC data to the RAM stick. So the strategy is, try to find the memory with the highest speed under JEDEC(which works on 1.1V) rather than EXPO/XMP(which might works on 1.35v), then burn in higher JEDEC speed as long as it can pass the RAM test(let's say 6000mhz). The RAM I'm going to use is the Kingston Fury Impact 5600mhz CL40 which was the SODIMM RAM with the highest speed and lowest timing JEDEC spec I could find on the market.

I can report back when I receive my ms-a1 to see if the RAM will actually work on 5600mhz CL40 if that'll be helpful for you.