D&D 5E The Mage - Casting Methodology that is the difference

[Sadrik]

Uhm... are you really asking? As I said, it's one prepared spell = one slot. It's when you don't actually even need to talk about "slots", when having e.g. 3 first-level spells to prepare means you can then cast each of them once, unless you prepare the same spell multiple times. It's how AFAIK core classes spellcasting worked in OD&D, BD&D, AD&D and how it worked for every core class except Sorcerer and Bard in 3e.

I agree, this does not have to be the 5e default but it should absolutely be an option. I think I would prefer it to be the default too. It is the simplest form of spellcasting out there.

Methods:
Classic Vancian
Neo-Vancian
Short rest slot recovery
Spell points long rest recovery
Spell points short rest recovery

Other possible ones:
Artificer/Alchemist/Runes put spells into things recover slots after thing is used