Confusingly, arcane feathers are physical/elemental ranged weapons that have nothing to do with the arcane stat and don't benefit from it in any way. Arcane is for spellcasters. When choosing your bonuses, pay attention to the weapon type and its damage element:
If you want to use a feather, you want bonuses to ranged weapon damage and whatever element the feather is. If you want to build the arcane stat and use spells, you want spell damage and spell efficiency (best obtained by being an alicorn) and whatever elemental damage spells you intend to use. If you want to use ranged lust weapons, you have a choice of two: The arcane taser (from prostitutes) and the arcane lightning globe (from Claire's teleport quest). In that case you want bonuses to ranged weapon damage and lust damage. These also don't benefit from the arcane stat despite their names.
In addition, spending all enchantment capacity on fire damage means there's none left for melee weapon damage. The scythe, being a fire melee weapon, benefits from both, and ideally you want to max out both the weapon type bonus and the damage element bonus.
Here's what a combat round looks like with +100% fire, +100% melee, and the soldier background:
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