The AXS15231 has some specific requirements. There are some changes to the driver that are in dev but not yet released. If you use the Dev version it should work OK. Alternatively for now add draw_from_origin: true to the display config.
The display update speed will be much better if you use LVGL instead of the ESPHome graphics functions. As you probably noticed turning on auto_clear slows things down a lot.
I have not yet found a way to build a graph the desired way using LVGL - so that the line changes color depending on the value of the “end-point” per hour (in a daily graph).
This is a graph of the electricity rates during the day - which was built in order to make it easier to identify when specific appliances should be started (washer, dryer etc)