I'd really like to understand what you're saying here, if you have a moment?
Does "going wide" mean targeting the top most keywords and "going deep" means targeting synonymous/descriptive terms for the successful wide keywords?
Going wide generally means going after similar, synonymous and descriptive terms.
Example: we are promoting auto loans.
"auto loans" is the seed/starting/initial/root keyword.
If we go wide, we think of what other keywords represent "car loans" in a similar way, synonymously or more specifically.
So, if we go wide, we will create terms like "car loans", "Mitsubishi loans", etc.
"driving loans" - similar/generic
"Mitsubishi loans" - specific
"auto loans" - generic
Then, we go deep on each of those.
For "car loans", going deep means, coming up with terms like:
"car loans in LA"
"cheap car loans"
"bad credit car loans".
Now, understand this: we haven't defined wide and deep for academic purposes. It is a strategy for building the best possible keyword combinations. So, sometimes, the boundary between these may blur.
An example in this case:
"small car loans" - can be thought of as going wide, since it describes the root keyword more specifically.
At the same time, it can be thought of as going deep on the keyword "car loans" as well.
So, in this case, we need to make a decision. Which will make more business sense?
People may type in depth keywords for "small car loans".
Example: "cheap small car loans", "small car loans in MA".
So, it may make sense to treat it as a "wide keyword" phrase, and then go deep on it.
Your strategy should be based on the tools and resources which you have for working with keywords. Not on some terminology like wide, deep, long tail.
It is all intended for running a campaign profitably - keep that goal in mind always.