Wow, that's already a lot of answers, thanks for that!
On foot, that can hardly be avoided. I have been car-free for 20 years (and that doesn't just mean I don't own one anymore, I also haven't driven one since then), and especially since I don't plan to drive to relatives' neighborhoods, we just have to shop on foot. Yes, a bike would also work. For now. In the next few years...
And for quietness, at the moment (also for over 20 years now) I live in a six-family house. Most of the time it's quiet enough, but every few weeks someone wants to drill, have a party, or make noise in some other way. Not to mention the daily "who can slam the apartment door the loudest" competition!
But I also believe that noise-wise a detached house that is a little distance (100m) from the nearest, preferably not too busy street, is quite quiet enough. It should definitely be quieter than what I have now. And if there's also a nice view from the windows, all the better, but that's really not the most important criterion.
In my opinion, all of that can be combined, but maybe not within my budget (although I think it's not too bad).
My idea with the islands is that if enough people live there, a certain infrastructure must be available (not every island resident can constantly go shopping on the mainland), that hardly any cars drive there, at least no through traffic, and on top of all that, the air is probably better (without exhaust fumes) and even the risk of burglary decreases because you can't just drive up easily and already be in the next federal state before the police secure the first traces.
What I haven't mentioned yet: from then on I will have a lot of time, but what I don't have is any manual skills; I won't (be able to) do renovations or remodeling myself.
And decide on the area first and then search there — I think that's the wrong way for me. Maybe I'm wrong, but I believe that each area can change so much after a few hundred meters that a "great" becomes an "impossible" (or vice versa).
The 113023246 already looks interesting, thanks Matthew03!