Only get a pixel if you want stock Android or the best camera in a smart phone. The quality and durability of the pixel cannot compare to a phone from Huawei, Samsung or Huawei. Plus THAT notch.
The iPhone camera is also quite good compared to oneplus. The plus side for the oneplus is that its the fastest and snappiest phone on the market. Plus the amount of ram they give will future proof the phone for at least 3 years. The OnePlus still has a nice camera just not as good as the iPhone or pixels.
I'd recommend not getting any phone just for selling, too much of a hassle but if you want to use them yourself then probably go for the oneplus or iPhone as i see you're not a fan of stock Android.
At 66k the OnePlus is a bargain against other phones and if you can live with a marginally worse camera that will still probably rival an iphone x in terms of pictures then definitely get the oneplus.
As for profit, iPhone is still the king