Paladin wrote:Do I have to do sth. concerning the layout or can I just ignore it if everything works?
Technically you don't have to do anything if you are happy with the device. If you experience problems you may wish to look at increasing the /system partition size or even switching to DataOnExt if you have a reasonably fast sd card.
Paladin wrote:How is this layout thing done? Can I use the HD2 toolkit software for this?
I don't know the toolkit but I am guessing there is a way to alter it in the toolkit. The file is a plain text file and can be modified with a text editor (not NotePad! Use Notepad++ on Windows)
Paladin wrote:Will my data and ROM be lost when I do this after flashing and configuring?
Yes, it will. Any time you re-partition. Make sure you have good backups.
You may want to look into TWRP instead of CWM as well.