Dear Brother,
Good to hear the adventure trip. It worth at least to see the variety of landscap. I highly recommend that you must have jeep for comfortable road clearance. The car is not out of question but due to the bad road conditions specially from Bunni to Mastuj to Laspur to Shandur is not good condition and it is the big test of your patience because speed limit will not be more than 20km/hr in case of car.
People travel on car on this road but not recommended and not advisable.
Regarding the road conditions,
1/ Upper Dir to Chitral to Bunni, you will find metal road but off course like hilly areas in some places some bad patches. The area is hot.
2/ Bunni to Mastuj, road but without metalling and you find mud/dust moutains and if you face rain it will be a problem for car. The area is hot.
3/ Mastuj to Laspur to Shandur to Phandar, its rocky road and rough. may face problem of road clearance in case of car. so for car drive you have to be slow in speed and be patience. The area is hot.
4/ Phandar till Gahkouch have metal road like of hilly areas.
Must stay in Phandar by any means its like heaven on earth.
This is all about. if you talk about about local people it bit confuse every body has its own opinion.
regards
Tabrez