Cloning a fully configured, "official" openwrt device best is done using a customized, fully configured firmware image, to be flashed to all the destination devices.
As Teltonika also provides a SDK for their "private" openwrt version, this should be the way to go.
I suspect, that quite a few Teltonika-private system pars are _not_ kept using uci.
BTW: Using a custom firmware image also has the advantage, to get rid of unnecessary packages. Thats the way to go for fleets of devices in an industrial environment.