Sanji isn't overrated. He been on balance on what he can do, Bogard. Also why you think Mihawk is underrated? Some think here he can beat off Yonkos and Admirals easily? He nothing, but overrated than underrated.
Garp overrated? Didn't we had him beating Rocks with Roger? Don't think he is overrated if Oda giving him great feat like that and capabilities in his prime.
Both Zoro and Sanji are Overrated in my Book by people who Overrated their abilities compared to yonko commander tier lvl characters when in reality the best they did is beat some mid tiers
I believe Mihawk is more Underrated than Overrated because Mihawk is a top tier, yet some people try to Underrated him by placing him as yonko commander tier. Top tiers are capable of giving each other extrême diff fight, when yonko commanders are for the most part low diff opponents, except few exceptionsI
So i value whoever win in a top tier battle less significant than underrating a top tier character to a lvl he doesn't belong to
I find Garp Overrated because most of hype not only come from government propaganda, but also against people who were far from their prime. He is placed on a pedestal he doesn't belong imo(Primebeard/Roger tier) when it's been implied multiple times in the manga that they were ahead of him in their prime