AC1200 model ex6120

Is it possible? Yes

Will it cause increased latency and drop your speeds? yes. 

Single and dual band extenders have to use the same chip to go router---extender and then extender----device. And they can't do both at once. So their speed is 50% of what they recieve. Add another extender to it and its at less tahn 25% of what your actual router speed is. 

Its why you see the push for triband mesh systems.