your forgetting ryou. until luffy shows he can use ryou effectively in g4 than his current base is his strongest form. I dont know if g4 will increase his adcoc either. awakening might be Luffys only way to progress past his current level and since he's reaching his limit as the gorsei are mentioning this legendary fruit then we have to take that seriously.
not that we can rely on odas words but he did say Kaidou won't be beat because of him getting hit hard.
You forgetting one important point, better attack means more potency, so Luffy using G4 would not just increase the attack power, but also would give a boost. As example, in G4 Luffy skin became very soft and hard in sametime. Doffy couldn't cut him anymore. I think this will happen here too with G4.
I mean if the attacks are not changing because of adv CoC, why Luffy used G3 last chapter and this chapter if he don't even directly touch Kaido? Well because G3 increase the Attack power,it is not just Adv CoC. Luffy combo his own strenght with adv CoC, more power means better Attack potency so yeah their will be a difference with Base Luffy and G4 Luffy. Oda will need a way to point this out. I hope with G4, Luffy using far bigger adv CoC shockwave or he combinate adv CoC in his punches to increase the attack power.
Kaido hit Kinemon with his Club too and touch him even thought using Adv CoC. Also Kaido hit and touch Luffy with adv CoC via thunder bague. You can still touch and hit someone with Adv CoC.
You will see,G4 will even push Luffy more now.