Like I said a real battle between them would be a long drawn out fight, if you believe otherwise youre kidding yourself. The ''time limit'' will magically not matter anymore.
Think he'll need another power up for that - G5's time limit's been lampshaded too often now as the only thing holding it back.
Looking at Oda's hints, manga Kizaru vs Luffy was strongly meant to parallel Kizaru vs Rayleigh back in Sabaody.
So I personally feel that old Ray is the best gauge for Luffy's mindset or seriousness.
What about Kizaru vs Kaido poll?
Probably favours Kaido and will become more one-sided as the arc follows.
Casual fans tend to be extremely partial to the OG Yonko in terms of powerscaling.
Side note
@Fujishiro the YouTube poll for Kizaru vs Fujitora went up to 10k votes and now 95% say Kizaru wins
Eh, Fuji hasn't done much of note yet. Once starts he starts going all Zatoichi on people's asses opinions will shift.
I still think Wizaru is stronger, but Fuji could definitely win.