Yes, that is correct. So if you were to look at the skeletal formula , you would be able to identify it exists as E or Z.
Only by practice, and observing that there are two different things attached to the atom that is also attached to the double bond. I don't think CH3
implies one form over the other (seem to recall in older literature that there may be on occasion an E or Z, or equivalent, typeset above the bond to help interpretations)