BTW, got any good info links for the F126 Saxony class?
You mean MKS180? That's still what it runs under officially ;)
Other than the latest cost estimate in September pushing it to 1.5 billion USD per ship... not much. Design requirements are basically identical to F125 with doubled flexdecks (with modules including ASW and MCM) and added AAW at minimum Layer 2 (ESSM Block 2) as well as a ton of growth potential in outfit (which F125 doesn't have, it's at its limit designwise from the start).
Since it's a design-to-cost project we basically only have the government's requirement set and the cost limit, and the companies can do with it what they want. It's by now basically a runoff between two consortiums, GNYK/TKMS and Damen/B+V, to build it.
Some design decisions are being taken outside the project itself, for example industry cooperation agreed upon with Norway as part of a submarine deal included the future standard surface-attack missile that will be mounted on MKS180 - basically an upgraded NSM derivative that will integrate German requirements on navigation and ECCM and have a range of minimum 300 km.
Sachsen/Saxony is the name of the F124 class btw, so MKS180 will not have that name.