I've had my One Plus 2 for nearly 2 years now, and I can safely say it's the best third party option I could hope for. Easily competes with flagships still, but at a much lower price point. Newer models are available too.
1+1 is by far the best looking phone I've ever seen and is something I'm looking forward into buying. (camera/flashlight position on the back cover is on-par compared to other models)
My phone is a Samsung Galaxy S7 Edge and the carrier is T-Mobile which in my opinion is alot better than AT&T and the phone works great and is alot better than my old apple phone which cracked with 3 months of use