My partner had a Megane E tech Iconic. Handed it back after 4 weeks. Firstly to answer your question on the HK sound system. It was decent, not as good as previous Bose & HK systems I have had in Audi & BMW but could still hold its own well for the size of the car.
It went back to the dealer after 24 hours for 9 days due to a well known alarm fault and the wires needing extra insulation above the headliner as the interference was setting off the sensors inside. The alarm would set off everytime you locked it and walked away. Very frustrating and embarrassing. The dealership were trying to tell her it would be weeks until they could get it in but we said we would leave the car at the garage as the alarm was disturbing neighbours and our children. Winter range was approx 140-170 miles at 100%. Charging speeds at the likes at Osprey were poor, charging curve is not very good.
I suggest you join the Megane E Tech Owners Club on Facebook and see alot of issues for yourself. It was nice to drive and comes pretty well specced for the AP but just was extremely frustrated with Renault service and it took the shine off the car for her. Hopefully they remedy a lot of known issues.