Will changing of SD card result in the loss of YouTube offline videos? I presently own an 8GB memory card. I wish to switch to a 16GB card now, but I do not wish to lose my offline videos. If I copy the .exo files, will it still be playable in the YouTube app? Or should I download it again?
To the best of my knowledge, and based on the Android device that I own (Samsung Galaxy Tab 2 ), the location of offline YouTube videos is as below:


  Internal storage->Android->
  data->com.google.android.youtube->files->Offline->(system generated
  folder name)->streams


Hence, switching to another SD-card (which is external storage) should not remove/delete your offline YouTube videos.

Just to be absolutely sure, you can first check the location of offline videos on your device (which should be something similar to the path mentioned above) and then you can proceed with switching SD-card.

But one thing you may note is, if you uninstall YouTube App's update, all the offline YouTube videos will be deleted. 

You may want to check more details HERE and HERE.