I've recently been struggling with the quality of my photoshop art. It has weird corners and just looks crappy when you zoom into the lines. I've tried all kinds of things, but they did not work.
I have applied a few screenshots of my current settings and appreciate your advice.
Your setting of 1920x1080 pixels gives you a total of 2,073,600 pixels or more simply you have roughly 2 million squares that you are drawing on (think of squared paper), this number will not change. Each square will hold one colour and when you zoom in the squares get bigger meaning it will become more jagged as you zoom in.
You can improve things by doing as Wardy said or looking for a program with an infinite canvas which should help reducing the issues