do domain spells use spell slots: Spell Slots in D&D 5e: All You Need to Know!. Best Sorcerer Spells for Every Level. Wizard 5e: DnD 5th Edition Class Guide - RPGBOT.
Not 100% sure on all domain spells, but all cleric domains in 5e received 1 known spell from class and one from out of class.
The Sorcerer gets more
spell slots than the Warlock, allowing them to focus more on leveled spells than the Warlock, who must use them sparingly and rely heavily on cantrips and invocations.
Each of these spells must be of a level for which you have spell
slots, as shown in the Wizard Features table. The spells are the culmination of arcane research you do regularly.