>>I'm not aware of a preference. "Anybody home?" for example, but then again probably "Did you check if anyone was in?"
>
>Not to mention that 'If anyone were in, I'd have told you.'

Now this is where N. American English falls down. That should be:
'If anyone had been in, I'd have told you.' - one step into the past is missed out in the 1st clause

If you're talking about the unlikelihood of anyone being in NOW:
'If anyone were in, I'd tell you.'

like that song "if I knew you were coming I'd have baked a cake"
-> "if I'd known you were coming I'd have baked a cake"

Another common one: "If I knew then what I know now" -> "If I'd known then what I know now"

N. Americans seem to forsake the past imperfect (or past conditional) for the past continuous at the start of the sentence then remember it exists at the end.

e.g. "If you gave me a gun I'd have shot him" should be either:

"If you gave me a gun I'd shoot him" (At this moment - implying it's unlikely you will) or
"If you'd given me a gun I'd have shot him" (last night, Goddam you) or
"If you give me a gun I'll shoot him" (chance you will)