Happy to help 
I’m not sure I understand what you mean so to be sure that you do not have a common misconception what a LSTMCell and LSTMLayer is I encourage you to gloss over this answer.
My confusion comes form what you mean by “one embedding at a time” and switching between LSTMCell and LSTMLayer - if it’s “one embedding vector at a time” then yes, LSTM (cell or layer) takes this as one of the inputs in each step. But if you mean one embedding feature at a time then no, LSTM does not move over embedding dimension.
Just wanted to make sure you understand this sequence because it’s almost the same for LSTM (except for inner calculations and one additional state).