Running 2x ZMACS with a ps100 7x4 Setup

Hello. 
   First question. I want to wire up a 7 head and 4 cab studio setup. There is a clear setup shown in the manual that is extremely helpful so thank you. My question is in my current workflow I am not planning on using a midi switcher to make changes. I would prefer to control my amp and cab selections via the selection switches on the front of the ZMACS. Do I need to tie the midi out of unit A to the midi in of unit B? How will the units see the state change of the other to make sure multiple heads are not selected at the same time or is this setup dependent on a midi controller to function as intended? 
 Question 2. I have a ps100 in the selectable attenuator loop of my current single ZMACS setup. I am running delay and verb through the FX loop on the PS 100 and there is a noticeable tonal shift (volume boost as well as additional bass) that happens when the PS100 loop in engaged. I have Tried with the FX on and off and the change happens in either state. Is there something I should be adjusting to rectify this?  

Thank you for your time. -Matt