The quality of the 7th gen. Civic was excellent.
The interior and the exterior both were excellent.
IMO the only thing missing in it were the Airbags.
I'll answer your questions one by one.
1: Regarding fuel economy the car is not that much fuel efficent, The best I got was 11km/litre with a light foot.
2: One of the smoothest shifting experience, Never had any such experience like gear stuck etc etc.
3: Yes, that was an issue and I was never able to set the handbrake according my my liking, It was good enough to stop the car from going backwards if parked on a slope but I was not satisfied with it.
However I believe that this was not a manufacturing defect and was most probably due to a worn out cable or some minor settings.
4: Excellent braking, no issue with the brakes. VTi has 4 Wheel ABS brakes where as EXi has 4 wheel disc brakes.
5: AC is excellent, However I also felt that Corolla,s AC performs slightly better but still the AC of Civic is excellent.
Coming to the difference in variants,
EXi was the base model with a 1500cc non VTEC engine.
It had 14" steel wheels with wheel caps,4 wheel disc brakes.
Interior was the same.
VTi was having a 1600cc VTEC engine.
It had 15" alloy wheels with 4 wheel disc brakes and was equipped with ABS.
VTi Oriel was the top of the line variant with additional features like sunroof,retractable side mirrors and adjustable seat height for the driver seat.
It had the same engine as in VTi.
Prosmatec stands for PROgressive Shift Management Technology.
It was the name give to the cars with automatic transmission.
So a VTi or an EXi with a Prosmatec sticker means that it is having automatic transmission.
Since you'll be looking for a used car so I'll prefer you to get the top of the line variant i-e VTi Oriel in good condition.
Now coming to the engine details.
EXi: 1500cc 4 cyl. 16 valve non VTEC engine producing around 110 hp.
Engine code d15y3.
VTi & VTi Oriel: 1600cc 4 cyl. 16 valve VTEC engine producing around 130 hp.
Engine code d16w9.
If you find a neat and clean one, go for it.
You wont regret your decision.