There are a few things to consider here, but lets start with the PAC Display question(s);
Yes, you can connect many (many) pac controllers to the one pac display runtime.
Yes, they can all have the exact same strategy.
This is possible because they have to have different IP addresses.
You only need to configure your controllers in pac term. Not pac manager.
You do not need to make a pac display per controller, any number of controllers can be in the one pac display.
You do not need to tick the option of allowing more than one pac display runtime running at once on the pc.
In this way, you can view all the controllers at once, on the one pac display screen if you chose.
Likewise, in pac control, you can have many controllers configured, just change the names and ip address.
If you are connecting locally, you just need to change the name, each controller can have the same IP address.
When you move from site to site, just open pac control and connect to that sites controller name. No need to modify the IP address.
As far as copying the same groov project to the different sites, cant say much other than subscribe to OptoNews.
The core of the original post is how each remote site is communicating back to the office?
Please do NOT do a port forward on each cellular modem to port 22001. This is in effect putting the controller on the Internet. You do NOT want to do this. It is a MAJOR security risk.
If you have not done it already, please read the guide to Networking Opto 22 Products. PDF Doc 1796.
If you are interested in having another groov back at the office (perhaps groov Server For Windows since you may have a PC there that is on all the time), then also consider reading PDF Doc 2161, Guide to networking groov.
Bottom line, hopefully the cellular modems have VPN clients or servers built in and you can set up a VPN at the office to connect to each of the sites.
With the VPN setup correctly, you will be able to use groov, PAC Display, PAC Control, PAC Term and PAC Manager all from the office to each remote site, all from one or more PC's.