That's strange, the default settings after installation provide the best balance between weather presentation and performance. ASN has been designed to provide smooth weather transition from one station to another, actually it was like that with AS2012 only now it has been improved even more.
In ASN tools tab ensure the "Cloud pop fix" is enabled in "Visual fix options." You can change the settings for download interval and increase it to the maximum of 30 min. (Default is 15 min).
Another thing to do is clear the shader cache in FSX, you can safely delete (make a backup) the Shaders or Shaders10 folder(s) located in C:\Users\Username\AppData\Local\Microsoft\FSX. You need to enable "show hidden files and folder" in your system.