I have developed a python app with Tkinter on a Mac. It involves forms, and canvas drawings. On the Mac, it looks great. However on my Dell laptop (4K display, and more powerful
The differences in the display of the same application are due to differences in render engines used by each Operating system.
This is coverd in a Pakt pub ebook called Tkinter GUI Application Development Blueprints
passage regarding this topic available here.
It may be a pain to do but it looks like the most common fix for this is to detect your enviroment and write independent styles using the external option database more info is available in the documentation here.