It's also called umlaut in English. x2config.ini doesn't have any parameters that need the umlaut, so that's not a reason for not using it.
Use EVTool to edit the BIOS instead of Kernelbasher.
The older 1.6 BIOS should work, but if it doesn't it's not a problem, because on the next boot you can select a different bank on the SmartXX chip.