@alikhan7 I agree with your approach. Try and learn on smaller cc bike first. It will tell you how your body and mind react on long tours and biking is your thing or not.
I won't recommend getting a bike lesser 125 cc. YBR G is more comfortable than GS 150 and yes it got looks too. You won't need to change tyres in YBR G as it already got good gripping tyres.
All bikes are under powered in Pakistan. Only CG 125 gives little speedy feeling because of its power to weight ratio but it lacks badly in safety and comfort.
YBR G can good you good cruising speed of 80 to 85 and i believe that is enough considering to Pakistani road conditions and traffic.
For bigger bikes don't yet think about it. just get yourself used to the first bike you purchase and get yourself engaged with some local YBR Groups there are many groups on Facebook you can search for some. Soon you'll get pros and cons of every bike.
and in future if you feel that biking is your thing and you have bugdet then go for a proper adventure bike. Like GS650F or Zongshen RX3 or even a good Trail bike from Honda or Suzuki. Don't go for inazuma CBR you'll waste your money.
Welcome to the biking world 