How do you distinguish between E1 and E2 reactions?
The only way to distinguish between E1 and E2 reaction is to do an experiment.
An E1 mechanism follows first order kinetics. The rate determining step is the loss of the leaving group to form a carbocation. So its rate depends only on the concentration of the substrate.
An E2 mechanism follows second order kinetics. The elimination is a single-step process, in which the leaving group exits at the same time as the base attacks. So the rate depends on the concentrations of both the base and the substrate.