I know that our X1C is WiFi only, I'm assuming that the P1S is probably the same.
Ours is connected to a local network to enable remote control from my desktop, but definitely not required if you just want to transfer files with physical media (SD Card). I believe that my DoD group physically removed the WiFi module from their P1S (no idea how easy it was to get to). I think that the X1E has a RJ45 jack, that might be worth looking into. Not sure what your needs are for offline-only, but if you're manufacturing ITAR controlled items, your ISSO will still probably require you to maintain a physical air-gap to be compliant.
I will note that we had to connect to an external network during the initial setup period for our X1C, I think for a firmware update.
I have nothing bad to say about the Bambu printer, it's incredible for FDM. My main use-case is fixtures, tools, and replacement parts. I typically print with PC or PAHT CF.