In reference to Gamma Gamma spend model, is this in any way related to Pareto/NBD, BG/NBD or BG/BB model?
The Gamma-Gamma spend model assumes that the expenditure of a client is independent of the transaction behavior.

Therefore, we can use this in conjunction with any CLV model. Models like Pareto/NBD and BG/NBD only predict the transaction behavior and client death (stops being a customer) independent of the spend value.