In my opinion:
Base Luffy (Gear 2/3) is High High Tier
Gear 4 Luffy is Low Top Tier
Gear 5 Luffy is Mid Top Tier
But when you add CoC, each Form jumps a Level, meaning:
CoC Base Luffy is Low Top Tier
CoC Gear 4 is Mid Top Tier
CoC Gear 5 is High Top Tier
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I believe Lucci is Low Top Tier & Kizaru is Mid Top Tier
Meaning Non-CoC Gear 5 Luffy > Lucci
And Kizaru > Non-CoC Gear 4 Luffy
For Luffy to push Kizaru to get All Out, He needs either CoC Gear 4 or Non-CoC Gear 5
But both probably Loss due to being Temporary & also Kizaru's Experience
Only way for Luffy to Defeat Kizaru is to go Gear 5 & Use CoC
But imo their Fight is gonna get Interrupted
And They will have a Round 02 in Next Island