I'm curious as to the actual difference in 1099 vs w2. If a contractor is willing to come in and work on schedule, must they legally be w2?

It's all about control. Those who control are generally employers. And the test for control differs from one governmental agency to another.   Many employers and employees think they can call themselves an independent contractor and that makes them a 1099 contractor. Not true.   Only the Department of Labor decides based on a complex fact based analysis who is or is not an employee. I have represented clients who they themselves believed were 1099s, who signed written contracts that they were independent, who the DOL determined were employees even though their pay rates for a year would have been a quarter million dollars and the 1099 contractor even decided their own rate of pay.   This misclassification can be very costly for an employer. Employment lawyers should be consulted.