Hi @jgskarda - the distinction you are seeing is not between Boron 404X vs. 404 but rather between EtherSIM and our previous non-branded SIM. All Supply Secure products (with an X at the end) run on EtherSIM, and some previous versions did as well.
Regardless we are actively working on expanding cellular coverage for EtherSIM and are evaluating adding both Verizon and U.S. Cellular support in the near future. Once we have a specific timeline in place we will share details here.