About the automation, I found a FAQ, it might be helpful https://www.tp-link.com/us/faq-1901.html

Hi Lerenzo, for this case, please check what's the topology of your netowrk? How did you establish the netowrk in your situation, just simple like from modem to Deco and the other deco is wireles...

Hi yes,all the deco can be work together , so it's not a problem for P7 and Deco M9 to work together