The key to this is that only a subset of settings can have local overrides (settings that differ between sites bound to a common Template). These are readily visible when you create a Template and bind a Network to it: they are the 'Configure' options that are still visible when you select the Network, not the Template to which it's bound. Configuration options that are only visible when you are managing the Template will have the same setting across all Networks bound to that Template. This commonality simplifies the management of a large number of sites. Bear in mind that you can have multiple Templates, if required.
The key local override relates to MX VLANs and subnets; in an AutoVPN config you configure in the Template, for each VLAN, a subnet of a size of your choosing (e.g. /24) from a defined supernet (e.g. 10.64.0.0 /16) Dashboard will randomly choose a free one from that range, for each new Network bound to the Template. Typically sites already have IP addressing of course, so you then go into the Network to change each VLAN to match the existing addressing for the site. This change is made once, generally by whoever is overseeing the implementation of the MX at the site.
A 'blank' Template will configure all bound Networks to have whatever is the default set of settings. Just because you haven't changed a setting, doesn't mean the Template isn't in control of that setting.
If the parameter you are interested in can be locally overriden, you can change it separately in each Network. If not, you can only change it in the Template, at which point that will be applied to all Networks bound to that Template.
