Bookowski,
A couple of other quick things I can say to watch for is, most States have a Modular Building Code that is separate from the local jurisdiction. Do to the enabling laws of the Modular Program, modular program's adopted codes control the codes used for the modular construction. Anything done on-site is to the local jurisdictions codes. As an example the modular boxes may be designed to 2015 I-codes, however, you are also designing for an awning that is done completely on site. That awning may be required to be done to 2018 or even 2021 I-codes, as that is what the local jurisdiction has adopted. Otherwise, check the destination State for modular programs.
Generally a design review agency is also going to be the inspection agency for a modular project. This means the inspection agency is going to be required to send inspectors to Europe to inspect the in-plant construction. Very few modular programs are allowing remote video inspections at this time, even post covid. So this is an additional cost factor may not be considered.
EIT, Modular Building Industry