Judging by the diagram used in the stream, the Pokémon transferred from Go to Home will only be able to move one way. This means that once you move to the Pokémon to Home, you won’t be able to move them back to Go, so choose carefully.
Given the ease of finding certain Shiny and Legendary Pokémon in Pokémon Go, this will allow players to transfer tons of rare Pokémon to Pokémon Sword and Shield. However, these Pokémon will have to be in the Galar-region Pokédex in order to be transferred. Other limitations between transferring from Go to Home were not made clear, if there are any.
Once you transfer Pokémon from Go to Home, you’ll be able to open the Mystery Box in Go, allowing you to catch Meltan. You’ll also get a gift of a Melmetal that can Gigantamax in Home, which is currently the only way to get this Pokémon.