Is disabling an app functionally similar to unistalling it? I don't know much about how apk and apps in android work.
Title says it all. In my specific case, I installed icon packs from a playstore app to be used along with Nova Launcher. Now I want to get rid of the app that provided the icons pack (it is occupying space). I disabled it with pm disble .. command. And the icons aren't gone. So, I guess, I'd be fine if I delted the app as well. but I am not sure. 

So, does uninstalling an app does more messing with the system than uninstalling it does?
Not disabling and uninstalling are different things. Disabling the app will let the it stay on your phone, but it won't be functionally working in the background/foreground. While uninstalling (obviously) removes the app completely from your phone. To use it you need to reinstall the app again.

Disabling will hide your icons in your case. For disabling the app, Go to your Setting &gt; Apps &gt; All &gt; Icons_Pack_App &gt; Disable. If you want to get rid of it completely and free up space, then Settings &gt; Apps &gt; All &gt; Icons_pack &gt; Uninstall.

You can also disable and enable apps with the command,

pm enable &lt;package name&gt;
pm disable &lt;package name&gt;