Also since modem stacks are so terrible - ideally two phones where one is just a hotspot for the other one and the one using the hotspot does not have a cellula

Also since modem stacks are so terrible - ideally two phones where one is just a hotspot for the other one and the one using the hotspot does not have a cellular modem. Also ideally not Android or iOS. Of course it is better to not be on the public internet with any sensitive device if at all possible. Anything on the internet is considered public.