Can Eevee breed with Gigantamax?
Unfortunately, players who were wanting to build an army of characters with this new form through breeding cannot do so. The community has discovered that the Gigantamax form does not pass down through reproduction, which means you will not be able to breed characters with this form purposefully.
Can Rillaboom Gigantamax?
Rillaboom has a Gigantamax form that was introduced in The Isle of Armor.