With Trunked systems, especially P25 TRS's, you get traffic on tg's when an user with an radio with that tg programmed in it affiliates with the site you are monitoring. To hear your local area, you want to put in just the sites closest to your location. You would only need the entire system if your going to be traveling all over the state, and will be traveling close enough to every site to monitor them. The more freqs you load into a scan pattern, the slower the speed of scanning multiple sites/systems. If your going to be traveling in certain regions, program in the sites that will be nearest your route, and destinations. For example, lets say your traveling from Hot Springs, to Little Rock, and back again. You want to put in the sites around Hot Springs, and the sites closest to the route you will travel along, as well as the Little Rock Simulcast, and surrounding stand alone sites. You don't need to have the Miller County sites, or Pope etc as your not going near them. Also remember, your scanner will "lock" on the site with the strongest CC and you'll only get traffic from that site. What you hear is determined by the tg's you program in the scan list, and the radios affiliated with the site at the time you "lock" onto it. Another example: You would rarely hear say Pope SO down along the LA State Line. And also remember, some agencies have their radios limited to certain sites to avoid overloading the system when traveling
Now, you can still fill up the whole shebang on the scanner if you want too, and just set up separate TSYS objects for each region your going to be near, and just lock those out when your not in that region. Or you could do it by travel routes..... Its really up to you.