Weihenstephaner vs Ayinger tours

I can't say about that specific walk, as I have never made it at night; but generally in small towns/cities in Bayern it's very safe to walk around at night, and streets are very well-lit.

For about the first year of living in Bamberg, I still looked over my shoulder while walking around town at night. It was only after a friend of mine decided to try and get her bike stolen (in order to collect some insurance $) by leaving it unlocked on one of the main streets in town -- and only finally being successful after 3 weeks! -- that I understood the extent of general safety there. That said, S-bahns themselves seem to attract trouble, with a lot of drunk kids looking for trouble riding them in the late hours, so be cautious there.

 

It's certainly safe, but the route I take runs through a gravel-path park that isn't as well-lit as the normal streets. There's a cafe along the way that would certainly light things up a bit, though. The sun sets pretty late, so you might even have a bit of daylight. I wouldn't really worry about it unless you have eyesight issues or any kind of handicap. If that's the case, the descent down the mountain could be a tiny bit treacherous if you take that route.

 

This is very, very true. While some people lock their bikes up, there are a TON of people that just lean them against things and walk off without a care in the world. In the heart of Munich you'll see full cases of beers sitting unattended behind the Viktualienmarkt stands...and nobody takes anything. People don't even seem to lock their car doors all that much either. We were scanning for the rare automatic transmission car (my wife pointed out that they aren't common) and noticed the vast majority of cars weren't locked either.
There are shady areas almost anywhere, but you're pretty unlikely to wander into most of them. In Freising I'm not sure there even are any.