How many spell slots does a Warlock 19/Wizard 1 have?

Question

I'm really confused by Multiclassing as a Warlock. Say I put 19 levels into Warlock and I have six spell slots. Simple enough.

The tricky bit is when you think of ways to get more spell slots. The most obvious way is to Multiclass into another spellcasting class - such as Wizard. If you look at the 'Multiclassing' area of the PHB, there's the following extract and a table for calculating spell slots when Multiclassing.

Pact Magic. If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know. — P.164 PHB

Thing is, does Multiclassing a level into Wizard increase your spellcasting class to lv.20 and hence by the table give you a massive boost of spell slots which can then be used with Pact Magic?

Answer 1

No, Warlock Spellslots do not count toward the Multiclass Spellcaster table

Spell Slots. You determine your available spell slots by adding together all your levels in the bard, cleric, druid, sorcerer, and wizard classes, half your levels (rounded down) in the paladin and ranger classes, and a third of your fighter or rogue levels (rounded down) if you have the Eldritch Knight or the Arcane Trickster feature. Use this total to determine your spell slots by consulting the Multiclass Spellcaster table. - PHB p. 164

Warlock isn't included in that list. Thus you would only have 2 1st level spells as a level 19 warlock, level 1 wizard PC. You could cast level 1 warlock spells using your wizard slots and cast known level 1 wizard spells using your pact magic. Granted you would be able to cast those level 1 spells at maximum level (as per usual with pact magic) but its not going to benefit you in comparison to Eldritch Master which allows you to double your spells per day effectively.

Answer 2

That is incorrect.

Right after the section on Spell Slots in the multiclassing rules is a section called Pact Magic

Pact Magic. If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.

Not only do you get to keep all your spell slots from both classes, you even get to use your Wizard Spell Slots for Warlock Spells and vice versa