The 396T will do control channel only programming. What it won't do, but the 396XT can do, is multi-site. For the 396T, you'd need to create a separate system for each site you need to program, including the talkgroups. Lumping frequencies from more than one site into just one system is unlikely to work. the 396T would stop on the first control channel it can receive, and use that until it can no longer decode that frequency at all. Even though you might have the control channels from one or more other sites entered as well, the scanner will not check any of them as long as it hears the first one it finds.
The 396T can use 700MHz frequencies. If this is the
system you are trying to hear, then you would not need to enter a custom band plan, The scanner would get that information from the control channel data. I know that a
firmware update was provided so that the 396T could handle rebanded frequencies. I could be wrong, but think that update is needed to allow the 396T to use the data provided by the control channel. MARCS is also a P25 system, so entering a band plan is not necessary. Again, that information is provided by the control channel.
The 396T also has lower specs on how many talkgroups can be entered in a system.