Can someone tell me how to change the font and font size used on the main screen?
You would have to change the size of the system font in the windows settings.
This freeware utility might be helpful:
Advanced System Font Changer from WinTools.Info
It supports profiles for particular applications.
Are you sure?
I don't think the 4 profiles are intended for 4 different applications.
There are only 4 different collections to choose from for various settings.
Or I'm wrong?
You are correct. Although you can create a profile that you choose to use only when running a particular application, the profile is not tied to that application in any way. Each profile affects the look of all applications on the PC, until you choose another profile. I was not clear about that.
Changing system font size doesn’t change the font in mp3tag. I am surprised that mp3tag doesn't have an option to do that. Now I can’t use it on my laptop, since font too small. No solutions?
Try Windows-Key ++
This would apply then to all other applications as well and the standard windows elements like menus, window titles, message boxes etc.
How do you cope with these?