If budget is an issue GM delivers the best product for it's price,
35-40 km/h with 90kg rider should be attainable with a 48v kit but also an 36v 16ah kit.
GM kits never appeared to not go trough costums, as they could be labeled as off road kits wich most
likely will be legal in Asia. (don't know for sure)
a front motor needs torque arms but make it easier to change tires etc. but with an rear one you don't wanne get a flat tyre, cuz it will take you a long time.
if you consider a MagicPie you should get an easy hour and a half to fit it to your bike, but only when you order the entire kit, I mean the one with a rim ans spokes.
but if you don't want to cycle you can use the cruise control, even if you pedal allong it will feel incredibly easy.
if the motor isn't used it could be a load especially with the 48v or the 36v 16ah, wich are quite heavy if you're not using the motor.
so if you aren't going to use it all the time a mini-motor with a freewheel should be appropriate. but as you life in a hilly place I won't suggest the mini-motor,
also the 1000w 48v or 750 36v is just an indication on what you're going to use not the actual power that will be delivered.
most likely on hills you will use about 500w max, wich is enough to get you over that long hill, but a long hill can also give heat problems so a motor designed for more heat like the 1000w 48v will be better,
15 min in a car, I would say get a 1000w 48v hbs with the 36v 16ah for better range but lower top speed, but the top speed should still be around 35-37 km/h. most likely 30km/h on the hills, if not to long.
a front 26 inch should be appropriate on a mountain bike aswell as the rear rack 002.
Here's is an indication of the price,
26" Front Wheel 48V/1000W USB Cable(External) Thumb Throttle No Pedelec 36V16AH + Charger + RAK-002
Item Number 26"FDEFS $739.00
739,00 usd WITHOUT SHIPPING,
if you ask nicely they will be able to do slow shipping wich will take a month more or so but will cost you 100usd less on shipping,
i don't know if this is still possible.
also an usb external cable to set the controller to your specifications.
hope this helps but eventually you got to make the decisions,
we can only guide you
cheers,
Hardcore