SCENARIO1 - "Or create a admin role only ties to that site?"

let's say you have 3 sites

site A
site B
site C
You can assign the Phone System Admin role to a user ext. and then select Role Domain: sites A and B.
This user ext. will have access to all Phone System settings for sites A and B, but will not see site C.

All phone System settings means they will see the Phone numbers (except numbers used by site C), they will see the Auto-receptionist settings(except for site C), they will see the Groups (except the groups of site C) and they will see the Phones&Devices (except for phones&devices of site C)



SCENARIO2 - Is there a way to give certain non-admin users that ability?
so this question is same as above, but the idea is for the user to be even more restricted, without access to the phone numbers, groups, phones&devices, but still having the ability to forward the site calls. This might be possible in a very specific situation - if the site calls route to a call queue. For example:

let's say you have
site A - routes to call queue A
site B - routes to an IVR menu
site C - routes to call queue C.

In this case you can have Standard User1 assigned as call queue manager for site A. They will see only the settings of the call queue(s) they manage -> They won't have access to phone numbers, Auto-receptionist, Groups, Phones & devices. They will be able to forward all calls by creating a Custom Rule on the call queue which would look like this:
Condition: 24x7
Handling: forward the call