Hello there and welcome!
Regarding the faint rattle during cold start, its not something ive ever heard on my own, timing chains are not a problem on the Mk7 but obviously timely oil changes are key to keeping the chain in good condition. Ensure it has good service history with on time oil changes.
It is normal for the oil to heat up quickly. On MK7 cars, the exhaust manifold is water-cooled, so coolant gets to working temp pretty quickly also. Not an issue unless oil temp gets too hot. Mine is tuned and runs a bit cooler but i believe it used to run at 106 degrees prior to remap.
My car (2013) also has that whirring noise (only noticeable when car in a garage, next to a wall etc) from the clutch and disappears when clutch depressed. Ive had VW check this and they say it's normal. If the bite point it good and it changes gear smoothly I would say it's ok.
Regarding the water pump issue, this is a well known issue where there is a leak from the thermostat housing which is a plastic unit housing the pump/thermostat. I had this chaged out at similar mileage to yours. Definately keep money aside for this one and inspect for any leaks before puchase.
The heater matrix is not a big issue on the Mk7 and the removal of the silicate bag from the coolant expansion bottle if not something I have done. You can search the forum and make your own mind up on that one.
The Mk7 is a fairly reliable car and IMO is a far superior vehicle than the Mk6. (aside from the steering wheel which i prefer in the Mk 6
)