Hi,
My advice ( being a owner of a RS7 C8 ) is look at the service history. see if the oil screen problem has caused an issue. The amount of oil and filter changes its had! I've been a owner of quite a few turbocharged cars in the past and as a rule of thumb, changed the oil and filter every 5,000 miles after using a engine flush. By this method I've not experienced any problems to date over the past 25 years. poor servicing can contribute to Turbo and engine damage.
Try and avoid chipped ECU's or excessive engine mods. I think the C7 model has a performance spec done by Audi to over 600HP anyway. The RS7 is a fast car with impressive acceleration. remapping and modding if not done right can cause catastrophic engine and turbo damage.
I hope this little bit of advice will help you in deciding.
Kind regards,
Lloyd