I doubt if there is much difference between the Gateway orbiting the Moon and the current International Space Station that has been orbiting the earth for a very long time as far as radiation etc are concerned.
There is a big difference—but the space explorers are going to have to learn that the hard way...
The Earth is protected by magnetic fields that protect the planet. The moon has no such protection.
The Space Station is below and is protected by much of the Earth’s magnetic field.