Are the structures with "in which", "which in" considered more formal than those ones with "where"?
That's the house in which I grew up.
That's the house which I grew up in.
That's the house where I grew up.

Question

Are the structures with "in which", "which in" considered more formal than those ones with "where"?
That's the house in which I grew up.
That's the house  which I grew up in.
That's the house where I grew up.

Answer

I'm not sure that any of them would be considered more formal. Grammatically, I prefer the first one, the second ends with a preposition, which some people don't like, and the third is OK.

Answer

I would consider the sentences to be formal, less formal, and informal and completely natural, in the order you have written them.

Answer

Ugh! "...and respected!"

Is there any way to EDIT comments/answers after posting them?

Answer

I prefer the third because it's shortest, it avoids prepositions, and "where" is for use with locations. I see this scenario as analogous to preferring "who" to "that" when referring to people -- pick the most specific word available for the job, especially with a word like "where", which is both commonly understood respected.

Answer

Yes, I know the rules. I suppose, your last sentence is the most common in spoken English. What about written English?