As stated previously, the sockets reduce signal integrity, which doesn't necessarily make them "bad," but is why Framework wasn't able to used socketed ram to maximize the potential of this CPU.
Basically, they need to use LPDDR5X memory, which isn't available in socketed form, because of signal integrity reasons.
Which means you won't see an improvement if you solder your ram directly, I think mostly because your home soldering job will suffer signal integrity issues, but also because your RAM isn't LPCAMM and isn't spread across a 256 bit bus.
This sort-of-interview of Nirav Patel (ceo of framework) explains in a bit more detail: https://www.youtube.com/watch?v=-lErGZZgUbY
Basically, they need to use LPDDR5X memory, which isn't available in socketed form, because of signal integrity reasons.
Which means you won't see an improvement if you solder your ram directly, I think mostly because your home soldering job will suffer signal integrity issues, but also because your RAM isn't LPCAMM and isn't spread across a 256 bit bus.