I'm not sure what you mean. Windows 7 is still supported, but I haven't used it for many years, so it's possible some things are broken, as I can't really test it myself. If you have any issues with it, you should report it on GitHub.

As for the renamed dll, one possible reason is that some security software adds ddraw.dll to the KnownDlls key in the Windows registry, which prevents all ddraw.dll wrappers from being loaded from the game directory. Supposedly, the Chinese security software "360 Total Security" is one of the culprits, based on this comment:
https://github.com/FunkyFr3sh/cnc-ddraw/issues/263#issuecomment-2035998859

Though as far as I remember, this issue can be worked around by using the InjectDll shim.

What you did has affected my whole system. Wow looks like shit now. I uninstalled HOMM 3 but the issue still persists. Can anyone help me remove whatever it was that was added in the patch?

I'm not sure what you mean, but DDrawCompat doesn't make any permanent changes to your system. Have you tried rebooting your PC?

of course. It's like the graphics got downgraded. They are less sharp and the it's almost like there's a haze over the screen. Also, the splash screens for wow are no longer full screen, just like the issue in HOMM 3.

If by "no longer full screen" you mean that there are black bars on the left and right side of the screen, then I already posted the solution to that for HOMM 3 in my first reply to this topic. Read it above.

I'm certain your issues with WoW have nothing to do with DDrawCompat however, and probably not even with HOMM 3 in general. All major GPU vendors allow you to set your display to be scaled by your GPU according to your preferences. See these articles for example:
AMD: https://www.amd.com/en/resources/support-articles/faqs/DH3-019.html
Intel: https://www.intel.com/content/www/us/en/support/articles/000058312/graphics.html
NVIDIA: https://www.nvidia.com/content/Control-Panel-Help/vLatest/en-us/mergedProjects/nvdsp/CS_Display_Scaling.htm

As for visual quality of WoW, I cannot comment as I don't have the game, but I'm sure it has nothing to do with HOMM 3 or DDrawCompat. Something else must have changed on your system.

If you're talking about the visual quality of HOMM 3, then check the DisplayFilter setting as I suggested in my first reply. If you don't like any of those options, then put "DisplayResolution=app" in DDrawCompat.ini. In that case, both the display filter and the aspect ratio will depend only on your GPU or monitor, depending on which one is doing the scaling.