I do free-lance editing, and there are differences between editing the work of a stranger and editing the work of a relative, like a spouse.
Some things stay the same; I am always careful not to make changes just to suit my style. I haven’t written this manuscript; it belongs to somebody else. But I don’t have problems taking out unnecessary commas, or putting one in where it is needed; of keeping verb tense consistent; of changing ‘shuttered’ to ‘shuddered’ when a character is cold - of making sure they really are saying what they intended to say.
When I edit, I try to give some guidelines to help them improve as a writer, so I won’t have to work so hard with their next manuscript. If I want them to change a sentence, paragraph, or scene, I explain why, and give at least one example of how (I think) it could be improved.
Strangers, so far, have been pretty easy to convince. Relatives... not so much.
There have been other challenges when editing for a relative that - so far - have not happened with a stranger. Like the time I was editing a 400+ page manuscript, and asked my relative to clarify/change a paragraph on page 151. He had already changed that paragraph and had apparently given me the wrong version of his manuscript. I had to start over.
Another time, I explained to a relative that when a planet’s moon is in the ‘new’ phase, it is (relatively) between the sun and planet, and so would not be in the sky at 1 AM, the middle of the night. I don’t think he believed me.
The difference might be a matter of perception. To the author who doesn’t know me, I am an editor, one who respects him/her as an author, and they listen and return that respect, especially if they are fairly new. To the relative, I am a sister, cousin, parent, daughter, or even a spouse. Yes, I’m intelligent, but they are, too, and while they love me, they don’t necessarily view me as knowing what I’m talking about.
Despite the challenges of editing the work of either a stranger or a relative, I would rather do that than edit my own work! Because in that case, I turn into an idiotic despot... on both sides.