I own BR-V, and I've been to Kalam, Nathigali, Malam Jabba, Patriata, Monal, Highland (this place is after monal called Highland with very difficult steep), and once from Hassan Abdal to Isb via Sohawa road with all the ups and downs.
I would say it's not under powered and won't say its the best, as I was able to climb easily with full load but only once I had to turn off the A/C because I felt that car was slightly struggling that time around we were 5 adults and 4 kids.