When using two monitors with different scales (e.g. 150% and 100%) under Settings > System > Display > Scale & Layout the size of windows is wrong (glazewm v3).
There are two different ways the window size is wrong. All windows are effected like described in Problem 1 and some are effected as described in Problem 2.

Problem 1

Normal windows only have the wrong size when they are created on a secondary monitor or moved to the primary monitor. After switching workspaces the size is corrected.

Problem 2

The size of windows like Task Manager, Registry or Task Schedular is consistently wrong. First thought that it has something to do with admin windows but normal applications that are executed as administrator are only effected as described in Problem 1 and there are other applications like GIMP (v20.10.32) that are effected even though not run as admin.

For this bug to occur the displays have to overlap in width or height (see image 1).

Image 1: Problem

When they are corner to corner the problem does not occur (see image 2).

Image 2: No Problem

Furthermore the size is only wrong when the effected windows are at the border between the two monitors.
Considering the configuration shown in image 1. When having two programs open next two each other, one effected (e.g. Task Manager) and one that is not effected (e.g. Command Prompt) the error only occurs when the effected window is on the right on the left monitor or on the left on the right monitor.

Example 1

Monitor 1: 100%
Monitor 2: 150%

Admin windows on monitor 2 have wrong height.
Normal windows on monitor 2 are 150% of the right height.

Example 1

Monitor 1: 150%
Monitor 2: 100%

Admin windows on monitor 1 and 2 have wrong size.
Normal windows have 2/3 of the right height.

I did some experimenting in order to understand the problem a bit better and gained the above mentioned information.
I hope it can help someone.
A thing that I have not really tested is whether the monitor resolution has an effect on this (I have used different resolutions).