Window frame of tool has the same dimensions in Win-MAC-Linux?

This is a bit of a weird question but I need to know if the floating tool window (:show_custom_dialog) has the same dimensions in the frame for the 3 operating systems Windows, MAC and Linux.

That is, if the top bar has the same height in pixels, or the side lines of the frame have the exact same thickness and if the bottom line also has the same thickness.

If we create a tool that needs to calculate the entire window surface and we use an operating system like Windows 11, we need to know if the calculations are going to be exactly the same for MAC and for Linux.

Unfortunately, I don’t have the necessary computers to test all 3 platforms.

I assume that all these dimensions are equal, but I have no way of verifying this.