In this segment we're dealing with prose, not dialogue.
That line alone gives you a very solid clue about my thinking, because dialogue, while not an 'anything goes' environment, is special.
Does that mean that prose is somehow unspecial?
No. It means that prose is different from dialogue. Prose requires better English than dialogue, because prose is part of the glue that holds the dialogue together. In prose we use our best English. We use it because we don't want the prose to stand out in any way as unusual. We want our readers to glide through the prose, absorbing what we show them, but without making their reading experience judder.
One problem is that my good English, your good English, and his good English have subtle differences. And we're each sure we're correct. As an example, I detest 'different to' because I've always been taught that the correct preposition to use is 'from'. Nonetheless I accept 'to' because it is in common parlance and because language is a living thing.
For creative writing this means, simply, that you need to be consistent, and as correct as you're able. Perfection, while desirable, is unlikely, and your readers will not require it. They just want their reading to be uninterrupted by judders.
When criticised for occasionally ending a sentence on a preposition, Winston Churchill replied, "This is the type of errant pedantry up with which I will not put." Churchill's reply satirizes the strict adherence to this rule. No one is urging you to write, "Where is Johnny at?" or "Where are you going to?" The best, most effective communication sounds and feels natural, and if that means writing, "Here is the file the list belongs with" instead of "Here is the file with which the list belongs," then write it that way.
That paragraph also contains a split infinitive, but, since it is in common parlance, we do not concern ourselves over it!
In other words, write your best English when you write the prose, but do not be puritanical about it.