The sandal has one inch wide webbing and the entire front foot webbing is one continuous loop.  The foot bed has medium arch support, it's more than almost everyone is used to in sandals.  The foot bed is a very durable rubber and has a diamond pattern along the full length of the footbed, (all chaco products have this diamond pattern on the foot bed.) My experience is that it the tiny diamonds don't bother the foot but they act as a mild abrasive.  The sandals run very true to size but if you are hesitant about fit I recommend trying out a brick and mortar store, my experience is that people often don't size up or down but more often they tend to swap from wide to regular widths.  The Z/1 is nice because it allows you to use socks if you wanted to with your sandals.  The Z/2 has a toe strap that adds a little more support but also has a more flip flop feel with a strap around your big toe.
The shoes are very comfortable and I have multiple pair of all chaco models now.