The lines should be determined by your height, weight and facial features. You've got to take good care of your hair, getting regular haircuts. It's worth paying for salon products. They tend to spend more on research and development and less on mass marketing. There also tends to be a more liberal return policy if you don't like it.
Relaxers are better than they've ever been.
They slow the speed of the curl down, changing from kinky curly to wavy. I like some of the relaxers from Paul Mitchell, Framesi, Paul Brown, Bantu and Audrey's. The basic active ingredients are the same. The differences are in the buffers and conditioners. They will not straighten the hair.