Need Help with DW, Trigger Happy, Fiend Patron Bladelock

[Cave]

When it comes to 5th edition I'm still a novice so I would like some help optimizing this build I was thinkering with.
Up until now I've played a Monk and an Arcane Trickster (using my spells for utility).
The idea is a Dual Wielding, Fiend Patron, Blade Pact Warlock that doesn't forget about all the cool fire spells he can get.
I'm going to be playing this character in an upcoming campaign and we already rolled for stats, my d6s blessed me with the following:

18, 16, 16, 15, 13, 11

I've decided my starting Race as the Variant Human, and I'm going to be starting as a Fighter for the Dual Weapon Fighting Style and weapon and armor proficiency.
I already know I'm going to take War Caster and Elemental Adept (Fire) as feats.

1) should I take Dual Wielder as my starting feat (delaying War Caster to Warlock 4) and if so should I go for max STR or DEX (rapiers)?
2) which cantrips, invocations and spells would you suggest? Remember this guy likes fire and doesn't shy away from using his magic.
3) this is not very clear in the PHB, if I chose to bind an existing weapon as my pact weapon can I freely change its form? (ex: can I bind a greatsword and change its form into a shortsword?) if I can, does the weapon keep its attributes and damage?
4) as a Warlock do I have to prepare spells like a wizard?
5) how does Armor of Agathys compare against Dark One blessing + Fire Shield?
6) can I make an offhand attack as a bonus action only after attacking with my main weapon or also after attacking with a spell?


Thanks in advance to everyone who'll take time to reply.

[Ewhit]

I can't give you all the questions but if u bond a weapon that's the weapon that you call u can't change it. Although it can be a dm discretion you would have to ask.

Strength or dex. The thing about pact weapon. It can be any weapon you choose if not a bonded weapon. So you can choose sword one moment 1 handed 2 handed . Mace another or flail or axe etc. awsome character concept visual but to do this you need str not Dex if u want hit dam bonus
Dex based is only rapier dagger scimitar for your choice if you want dex hit damage so you limit yr choice now if this limit doesn't bother you for visual weapon options dex is best ac initiative and fines weapon

Take duel wielded first if u want that style first. Of having same weapons in each hand. So at lvl 1 u can rapier then rapier again for off hand and then u can action surge a spell or sword
Ayes you have x amount of spells a you memorized but can only cast 2 per short long rest.

Can't tell you what's best armor agyth or dark one blessing. Simple view is do u want concept to have no armor then get armor age th if yr going to wear armor go other way.

[CaptAl]

When it comes to 5th edition I'm still a novice so I would like some help optimizing this build I was thinkering with.
Up until now I've played a Monk and an Arcane Trickster (using my spells for utility).
The idea is a Dual Wielding, Fiend Patron, Blade Pact Warlock that doesn't forget about all the cool fire spells he can get.
I'm going to be playing this character in an upcoming campaign and we already rolled for stats, my d6s blessed me with the following:

18, 16, 16, 15, 13, 11

I've decided my starting Race as the Variant Human, and I'm going to be starting as a Fighter for the Dual Weapon Fighting Style and weapon and armor proficiency.
I already know I'm going to take War Caster and Elemental Adept (Fire) as feats.

1) should I take Dual Wielder as my starting feat (delaying War Caster to Warlock 4) and if so should I go for max STR or DEX (rapiers)?
2) which cantrips, invocations and spells would you suggest? Remember this guy likes fire and doesn't shy away from using his magic.
3) this is not very clear in the PHB, if I chose to bind an existing weapon as my pact weapon can I freely change its form? (ex: can I bind a greatsword and change its form into a shortsword?) if I can, does the weapon keep its attributes and damage?
4) as a Warlock do I have to prepare spells like a wizard?
5) how does Armor of Agathys compare against Dark One blessing + Fire Shield?
6) can I make an offhand attack as a bonus action only after attacking with my main weapon or also after attacking with a spell?


Thanks in advance to everyone who'll take time to reply.

1. With your rolls you can go Str or Dex and be effective. If you envision a brute in heavy armor go Str. If you envision a skirmisher in light/no armor, go Dex. Warcaster can wait until 4th level. With your concentration check likely being at +5 you shouldn't lose spells often.

2. Take Eldritch Blast for an effective ranged at will. Fluff it as tiny fireball blasting people in the chest. Invocations are for fleshing out your character, and filling power gaps. Devil's Sight is awesome, especially as a human without darkvision. Also, especially at lower levels, Hex will help your DPR out a lot. Just remember it uses bonus actions to cast and move around limiting your ability to swing both weapons.

3. I wouldn't allow it. If you bind a weapon, then that's your weapon, IMHO. Ask your DM, he/she may be more generous than I.

4. Nope. You get a certain number of spells known. Those spells are available to you in any combination until you use up your pact slots.

5. I haven't done the math on those. I won't try to give advice on something that I'm unsure of.

6. Two weapon fighting requires the attack action to get the bonus action. So, no spell then bonus action attack. Eldritch Knights using War Magic (Starting at 7th level), and Valor Bards using War Magic (Level 14) can cast and slash in the same round. You can also Haste yourself in round one, and round 2 cast a spell with your action, then use your haste action to attack which enables the bonus off hand attack.