Separate +12V to Kincony, +24V to MOSFETs

[Toper]

Hi,
I have a question about power supply for T128.
I'm using 24 V relays (Finder 40.52) connected to the Digital Outputs.
I am considering two power options:

1. Two power supplies (this version works fine since 2 days):
   
   • 12 V for the Kincony board (VCC),
     
   • 24 V only for the outputs,
     
   • common ground (GND) for both power supplies.
     
2. One 24 V power supply:
   
   • 24 V connected to VCC and to LO.
     

My questions:

• Is it safe to connect the grounds (GND) of the 12 V and 24 V power supplies together?
  
• Does the manufacturer recommend using a common ground in this case?
  
• From thermal and reliability point of view, is it better to power everything with 24 V, or use 12 V for VCC and 24 V only for outputs?
  

Thank you in advance for your help.
regards,
Toper