Would it be correct if I rewrite this sentence 'Search for what is the real strength' as 'Search for what the real strength is'? Does anything change?
Yes and no.
But isn't it an indirect question? Shouldn't it be subject + verb + obj.? As ' I want to know where you come from'?
How would it be in current usage?
In current usage, "where you come from" is far more common than "from where you come."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.