I think garp is overrated.
Here is what i think because garp had been in famous incidents like the rox or rocks and some other fights and made it alive he made a name for himself as an after-affect.
This doesn't show anything like for example let's pretend i am in one piece as a character right?
So let's say i fought in the marineford war and made it alive so i made myself a name where at some point everyone will think because i survived that war i am let's say super strong but in fact i could even be super lucky i was alive like maybe someone helped me survive or i was hiding in buildings like a coward.
But no one will know that, every outsider will know i was in that war where they fought strong guys.
Garp could easily be barely alived in those incidents and could easily be saved by roger where roger beat the big baddy and garp just because he was in that fight he got a name for himself.
The guy displayed only armament haki and punches.
Not sure if he has observation but if he had observation he never used it and i do not think he got kings conquer haki otherwise he would have used it as well.
This can easily be implied to every character literally it is the so called faked hype through others calling stories of how strong specific characters are.
we do not even know if he could beat shinki the golden lion alone i would say they could easily be lucky by using seastone cuffs to neutrilizing shinki and beat him he also had sengoku's support so i have this feeling that garp in his prime wouldn't be able to even beat rob lucci of today.
Like if garp's could only beat guys of don chinjao tier well i would say he was definetely not equal to roger or whitebeard and if i would give an overrall strength rate , these guys would have been at 10 and garp barely at 6
He is the real deal but from the combat standpoint, Oda hasnt given him anything that would allow him to be equal to weapon users or DF producers.
That's why his encounters with swordsmen like Rocks and Shiki are off-screened. Same reason Zoro vs Luffy was hidden behind the mist. Simply, hands are inferior to swords. Oda would compromise his own work if he made the hands equal to swords.
Garp's body is nothing special, regular human body like 99.9% of other OP characters. He was hurt by MF Luffy and by captain Morgans.
Sengoku the Buddha, is better equipped against weapon users or DF producers, his body is made of gold and he has shockwaves to keep the enemies at distance or at least put a pressure on them and reduce the effectiveness of their attacks, likeFujitora's gravity, extra weight on the opponent so to say...
What Garp can do to shield himself against weapons and DF produced mediums is combining all techniques to lower the damage. There are things like Hardening, flow blasting and tekkai and when combined they could possibly lower the damage enough so he stands a chance instead of being one-shotted. However, Oda may only have hinted towards Hardening only since Garp hasnt demonstrated anything else and his prime training to beat someone like Chinjao doesnt really help Garp's power level and also, entire God Valley is off-scened as well. His best on-screen feat is punching Marco and doing nothing.
prime Garp is PK leveled.
I am pretty sure the story was clear that PK is a navigational title, the one who finds the last island and the treasure, not a power level title.
If you think of it as PL title, then it scales to those who find the treasure, for example, if Buggy finds it, PK would be Buggy's level.