Someone know if it's possible to change the color of a pixel in a canvas without using un object, so without using something like canvas.create_oval or canvas.create_rectangle ?
There is no way to color a pixel other than to create a 1x1 pixel object of some sort. And yes, at some point you will experience performance problems. The canvas simply wasn't designed to be used this way. 
If you're really needing to create a large area in which you can manage individual pixels, you can create a canvas with a single image that is the same size as the canvas. You can then set the color of individual pixels on the image through the photo image interface.
Change the color of a pixel in a canvas, Tkinter, Python