Magic initiate and multiclass spellcasters

[Iampower]

Lets say that bob is a 2nd level cleric and a 3rd level wizard with magic initiate-wizard.
As per The Sage, bob should be able to use his wizard spell slots to cast his magic initiate spell if he prepares it.
But as a 5th level musticlass full caster, he has a different spell slot table to look through.
The question is, can bob use all of his spell slots to cast his the magic initiate spell, or is he limited to what his wizard spell slots would have been as a 2nd level wizard or something similarly silly?

Edit: i wanted a clarification since RAW says you "use your <<CLASS>> spell slots to cast your <<CLASS>> spells" and multiclass rules didnt seem to clarify if the upcasting part of the rules extended to how the magic initiate spell was worded.

[Mitsu]

I just let players cast Magic Initiate spell from whatever spell slots they have, even if it's from another class. As long as they are casters- they can cast it from whatever slot they want.

As for RAW- by RAW when you multiclass let's say Cleric 3 and Wizard 5, you are level 8 Caster. And if you know Fireball spell, you can cast it from 4th level slot even if that slot is only from multiclass.

So MI spell works imo the same. You can cast it from whatever slot you want as long as you have class associated with feat. So even if you are Wizard 2/Cleric 18 you can cast Wizard spell from MI from maximum slot as you are Wizard after all.

That is how I see RAW. But I think the whole Sage advice as for MI is stupid, so I just treat MI spell as just new spell learnt, no matter of class.