We have a similar situation, although our full repayment loan has a worse interest rate (1.77%). For us, it will probably be a combination of a 15-year loan + NRW.Bank full repayment loan. I can understand your decision. It's just the safer option.
Some other things were more important to us (interest-free period, repayment change, flexible use of equity -> no priority for the equity)
Nevertheless, I will have the 20-year and 15-year calculations done again, for the feeling, and I am currently trying to get the interest rate for the 15-year loan a bit cheaper.