Yes, when crossing the border between two countries covered, all Digital Republic SIM cards allow smooth connectivity. Please note that for this you need to have a roaming data package deposited in advance so that it will be activated directly.
NB-IoT generally does not support the so-called "Seamless cell handover", i.e. the smooth flow of connectivity during the radio cell change. In this case, the connection is terminated and must be re-established.