I have always bought low milers in the past but on this occasion bought the B8 with 105,000 on the clock over 2 years ago.
Has hardly missed a beat, but has been meticulously maintained by me and the previous owner.
The only real niggles have been the replacement of a PCB on the mechatronic unit and an oil breather pipe. Both are apparently not uncommon faults and fortunately neither are expensive fixes, especially when you get a goodwill contribution.
I have not had any issues with any of the points you mention, and you certainly don't need to worry about costly failures of the likes of turbos or DRC on these cars.
Perhaps I should add that the car has been running MRC stage 2 for some 2 years/18,000 miles, again with no issues.
It's often said that these cars are over engineered and good for 250,000+ miles. There will of course be exceptions but I've not heard of an horror stories yet.