GTI Options
From my experience of nearly 4-years with a MK7 GTI PP and now a couple months with a new Mk7.5 GTI I would suggest you consider the following.
1. PP
2. DCC though not essential but does give more comfort.
3. Xenon headlights
4. Reversing Camera
5. Key-less entry ans push button stop/start though not essential.
6. Climate control is nice.
7. DSG
Just one word of warning and that relates to the rear shock absorbers on the non-DCC MK7. The are not good and can make an irritating type of knocking noise. A very large amount of owners had problems with these and subsequently replaced these with what I recommend back a few years ago. I suggested the Bilstein B4 shock absorbers as for me and many others they made a very immediate and noticeable difference. Take a look at my website relating to this issue.
www.vwgolfmk7problems.uk Of course you can fit whatever you like but as a low cost OEM replacement this is a great shock absorber.
I recently purchased the MK7.5 and even with this "new model" the rear shock absorbers are still to some extent noisy. I have now fitted Koni Active's and those made a really good difference to ride quality and they are silent.
Another point and that relates to tyres. If whatever you buy is fitted with Bridgestone Potenza S001 tyres then replace them as they are as hard as hell and noisy.
I see you are considering the MK7 and not the face-lifted 7.5. This is a good choice as having now driven three Mk7.5's I can tell you that for me they are disappointing in terms of road and cabin noise when compared to the original MK7. The GTI 7.5 is definitely not an improvement on its predecessor apart from the cosmetic nonsense and fancy infotainment unit and dashboard. Given a choice I would swap the 7.5 for my original Mk7 in an instant.
To anyone considering a Golf 7.5 I would suggest they drive that model and really listen to the cabin noise and then drive a MK7 as to me there is a significant difference. Would I buy another MK7.5 - definitely not. Would I buy the MK8 - possibly but VW would have had to make significant improvements to reduce cabin noise.