I could sense a degree of dissatisfaction or frustration from you with the Kapex, which of course can be due to many factors. Kapex is best known for its precision and accuracy (assuming proper calibration is checked or done by the users (again, Gary Katz has shown how to do that)) among other things (motor issue one of them!). There are many Kapex videos out there one can search about how good it cuts miters or angled pieces. Peter Parffit, a hobbyist, has done many videos and here is one I found:
https://youtu.be/FemIf5O0mXQ?t=208
Even though I have no images to share, please be assured that my Kapex performs as well as (if not better than) his in all aspects.
If you aren't getting good results, I recommend that you review Gary's videos
AFTER checking that your saw's table and fences are flat, straight and square to each other (and of course that the blade cuts true). I have not come across any miter saw calibration method better than Gary's (Kapex was used in his calibration videos).
Simon