Can a W2 contractor be paid salary vs hourly?

There is something not quite tying together about your question: a W2 is used for employees (who may be paid either salary or hourly at the employer's discretion), whereas a "contractor," or more properly, an independent contractor, has his/her compensation reported on a form 1099. A contractor can be paid on any basis to which the contrator and employer mutual agree, or "contract" (as the term "contractor" implies)--e.g. hourly; daily rate; salary; per project; etc. There is no such thing as a W2 contractor: either you are an employee and get a W2 or you are a contractor and get a 1099. Again, though, you can pay either an employee or a contractor on any basis.
The test for whether a given worker could be considered a contractor or must be considered an employee is based not on payment method, but on *control*--how much control the employer exercises. You can find a detailed discussion on the U.S. Dept. of Labor website, but in brief, if you set the worker's hours, determine where they must do their job, and can tell them how to do their job (instead of just telling them what the job is, then letting them get to it), they would very likely have to be considered, and paid as (including wage withholding, benefits, overtime as applicable, etc.) employees.