Do something in hook_node_load only when displaying node Is there a way to run a specific block of instructions in hook_node_load only when the node is loaded do be displayed and not when it's loaded in the edit form?

The only way I can imagine is analyzing the url and if the pattern is node/%/edit don't execute the code.

I know I can also use hook_node_view, but in this case I have to add render arrays instead of simple values
Yes, you'll need to examine the URL for this.

Loading a node is (correctly), completely de-coupled from displaying a node. node_load() doesn't know what you've loaded the node for; it doesn't care, its only responsibility is to prepare the node object.

So the context you're looking for doesn't conceptually exist when hook_node_load() is invoked, as that by definition has to happen before the object is passed to node_view(), and there's no way to signal your desired intent to node_load()