Brother,
If you want a good smartphone under 15k for heavy usage,nothing can rival the performance of Xiaomi Redmi Note 3.It heats less,gives consistent fps(due to new SD 650) ,one of the best display in the segment(behind Zuk Z1) but camera is just average and Xiaomi have very poor service in my place.
Next phone to consider is Lenovo Zuk Z1,which give an above average gaming performance,best display among all phones in the price bracket and also great battery life.
Also consider Moto G4 plus besides it faces frame drops and heat much more than others.It's not that bad for gaming as u might think of.
I just don't know regarding brands like Samsung for gaming in this price range.It's a fact that their expensive phones does a great job but lower priced sibblings doesn't excel well.I don't know more regarding it as i never had any hands on experience with those phones.
Hope this might be useful.Forgive me if there is any mistakes as i just want to share my ideas with you so that it might be useful to someone.
