There is one more, higher rarity item that you can earn in Call of Duty: WWII: Heroic.
Users have been sharing images from their Supply Drop openings and showing off a red-colored rarity of Heroic. The voiceover in game even acknowledges that Heroic item.
From what we have been able to see, Heroic items are exclusively earned through Supply Drops. The Collections only show you the ability to earn the Epic variant of each weapon, not their Heroic variant. As noted, all variants have no actual stat changes — just cosmetic variations and XP bonuses. There are also a number of Heroic customization gear sets available to earn in Supply Drops.
Images via @OnlyIncxte and @AwSoMeWoWzz