I'll call an archetype as consisting of the groupings they list at the base of the cards on the wikia. There is one exception, that I'll term the monarch exception.
The Monarch Exception) Where it is so blatant that they should be merged that there are two groups with the same name and only differentiating by essentially one being a monster while the other is a spell/trap, oh god why, the two should be considered as one and the same.
Subtypes (ex. Meklord, Meklord Emperor, Meklord Army, Wisel, Wisel Attack, Wisel Guard, Wisel Top, Skiel, Skiel Attack, Granel, and ∞. (I have no words.) Exodia and Forbidden One. D/D and D/D/D) are included in the Monarch Exception. If there is a case of an archetype listed by monster type, I will count the subtypes as separate.
In the case a card belongs to multiple archetypes and the two don't fall into the Monarch Exception, it belongs the most to the one it is a member of. If it is a member of neither, then you declare which one it will count for, and will only count towards that one.
I see. So, everything listed as a member, support, or related will count towards the archetype max, and type or attribute decks are ruled out since archetypes are a separate grouping system based on card names. I'm guessing the "Monarch exception" will also apply to interlocked archetypes that mutually support between the two. I'll...keep trying to build a deck that has a good feel, I suppose.
Fluff means nothing in deck building terms. So Future Fusion wouldn't count as E-HERO, but instead...why? Oh god why? What the hell's the difference between fusion and polymerization? It falls in the Monarch Exception, but still!
The Japanese name of the card is 未来融合-フューチャー・フュージョン. This essentially albeit inelegantly translates as Future Fusion - Future Fusion, so it's clear why they changed it, but how they changed it resulted in a bit of a side-effect. Its original name makes it a part of two archetypes: 融合 (Fusion, translated as Polymerization) and フュージョン (Fusion, translated as Fusion), but this particular quirk was lost in translation. That said, there is no support card that distinguishes between the two archetypes (the only one that works on both is
Synchro Fusionist, which declares both archetypes irrespective of language), so it's largely semantic in this particular case.
By the bye, this reliance on Japanese names for all archetypes in order to ensure consistent rulings when combined with archetype rules for the game also results in many other oddities. For instance, Dif
fusion Wave-Motion is not a Fusion card in spite of technically having "fusion" in its name, not because it would make logical sense for a spell with absolutely no ties to fusion-summons to not be tied to fusions, but simply because its Japanese name doesn't have "フュージョン" in its name. On the flip side, certain archetypes (such as Prophecy) may include very odd cards in it that have absolutely no ties to the archetype (
Armor Exe), because in the Japanese names, the archetype name is contained in the Japanese name for that card.