I am also currently in the process of finalizing my financing...
I have a few "own" opinions on this:
I find the "security costs" very high. The interest surcharge, especially in the first months (years...) of financing, is enormous. Especially then, you should repay as much as possible.
What awaits us in the future? The EU is currently in an interest rate trap. Example: Japan. Draghi and the ECB will soon not dare to raise interest rates too much. Among other things, EU countries cannot afford to bear higher interest rates on government debt. So what awaits us: an interest rate level around 0% or very high inflation (also called hyperinflation)... I tend more towards low interest rates...
I have decided to split the total debt into different contracts (depending on duration). That way, I am at the bank every 5 years and can almost always react to market developments...
Regarding [WohnRiester]: For me, it is not worthwhile at all (at least I have not found any positive features yet). Above all, I do not want to receive a repayment bill in case of a nursing home situation. This way, I am much more flexible...