The C1 and C2 ports are used as an uplink ports only.
If you go the stacking route (X1 and X2) this would mean that you would manage the ICX switches effectively as one logical switch as opposed to the uplink route (C1 and C2 ports) where you would have to manage two individual logical switches.
Power management is based off the physical switch itself (depending how many POE devices you connect) so stacking would not really have anything to do with managing power between the POE devices except for assigning the power-by-class commands.
Based off your proposed diagram (if this is how you would prefer) then you would not need to use either the stacking nor uplink ports as they all go back to the router which I would assume is your core.
Thanks Marvin - much appreciated. Assuming I don't overload the Power, presumably I can just use the switches as "plug n play". Do I even need to use the C1 and C2 as I assume there's a management page I can access to my PC which will be wired into the network. Many thanks from a switching novice! Peter
Yes you can use it as a plug and play as it would use the default VLAN on the switch (VLAN 1).
Assuming you have not configured any specific VLANs, the C1 and C2 ports can be used as uplinks to the core thus leaving an additional ethernet port free for a computer or whatever else.
Generally speaking you can console into the switch (using the console cables provided with the switch) to manage it via CLI (which I would recommend trying to learn - this goes a long way down the track).
All ports on all Ruckus switches can be used as uplinks (towards the network core) or as downlinks/edge-ports (towards the end devices), so you can use C1 and C2 for either. The only caveat is that they do not have PoE but this means that they are ideal to use as your uplink(s) to the router leaving the 12 PoE ports free for edge devices. X1 and X2 can also be used as data ports as well as the stacking option.
Stacking would allow the two switches to be managed as a single device and potentially provide some resiliency benefits if your router supported LAGs but there are costs involved, stacking is done over 10G links so you would need to upgrade the licenses on the switches to support 10G and also purchase 1 or 2 twinax cables.Given the simplicity of your set-up I would not bother and just manage the two switches individually.