Hi there,
RUTC50 would be considered a router, i did think you are considering those too.
In regards to the mobile modem, all you should consider, with which mobile bands, does you Sim provider work. In the device details on our website, in ordering section you can find with which mobile bands, what product code device works. TRB500 5G Gateway
If you are only considering a gateway, then yes, TRB500 or TRB501 are your only options from our portfolio.
You can read more about the difference in this thread : Differences with Mobile Modes (NAT, Bridge, Passthrough) as another user has already asked this question.
More information about these modes can also be found in our Wiki : RUTX50 WAN - Teltonika Networks Wiki
Which mode to use, depends on how you want your network to operate.
Regards,
Arturas