It's still stressful but nowhere near as stressful. For instance - employees get a salary, founders usually don't. That alone makes a huge difference. The founder has to keep the startup alive, try to find funding, direct the product all while one bad decision could kill it. The employee has to do what the founder asks, do it well, and go home at the end of the day. Being an early employee is still more stressful than a normal job especially as there is no one to help out if you're stuck, but I think the difference between founder and early employee stress is vast.