Technically speaking (following the checklists that you can find), most Crossfit coaches probably should be paid as employees. That said, I'm of the opinion that being an IC is always better. I want control of my money, I'll pay my taxes, when and how I feel is the best way. Generally speaking this is a zero sum game. Do you want to be paid $20/ hour and have the gym with-hold taxes, or do you want to be paid $25/hour and you as an independent adult make your own decisions on how to handle your money. I'm way over-simplifying here obviously. I've been both an IC, and employee, and a business owner that has paid IC's and employees.

The exception here would be if they are offering some huge benefit as an employee that you are not getting as an IC (like health insurance) - but that would not be the norm for a Crossfit gym.