You have quite similar methods for reading the config in Yireo_GoogleTagManager_Helper_Data as well as in Yireo_GoogleTagManager_Block_Default. This should be unified. I suggest keeping it in the helper and call the helper methods from the block.
Sigh, legacy code. Good point. I will look into this soon (but am busy with too many things at this moment) and will leave this issue open until it is fixed.
You have quite similar methods for reading the config in
Yireo_GoogleTagManager_Helper_Data
as well as inYireo_GoogleTagManager_Block_Default
. This should be unified. I suggest keeping it in the helper and call the helper methods from the block.