Iron Fist or No Guard for my Golurk?

Question

I'm thinking something like this:

Golurk
Go-Lurker (Thanks Jar/ Sempi for the nickname!) (Golurk) @ Choice Band
Ability: Iron Fist/ No Guard
Shiny: Yes
EVs: 164 HP / 84 Atk / 128 Def / 128 SpD
Adamant Nature
- Dynamic Punch
- Earthquake
- Shadow Punch/ Phantom Force
- Heavy Slam/ Gyro Ball

Answer 1

If you're planning to keep Dynamic Punch, always go No Guard as Dynamic Punch is worthless without it.
But if you are willing to replace it for something like Drain Punch, that will be boosted by Iron Fist, that would be the only reason for you to give it Iron Fist.
So yeah, if you're keeping Dynamic Punch go for

No Guard

Answer 2

No Guard

No real competition here, No Guard is the main reason you're running Dynamic Punch, otherwise don't use it. Even if all other moves have 100 accuracy, 100 accuracy No Guard is too good to pass up.
Only two of your moves get boosted by Iron Fist, another reason to go for a No Guard.