Didn't Brannew say that the red hair pirates have high average bounties and are considered the most balanced among the yonko?
As Shanks so far appears to have the smallest yonko crew, it would be pretty believable for me that Shanks crew members have higher bounties than compared to the Big Mom Pirates and Beast Pirates and their commanders to even things out. Not to mention the fact that people like lucky roo, Beckman and yassop get more time to shine when your crew isn't in the 20, 000 member figure like Kaido or Big Mom's. There leaves more opportunity for individual members to get the headline news when your crew isn't overcrowded with people and don't have to look through hundreds of bounties to find the star of the show.
Though having said that I doubt the sweet commanders and the calamities are 2x weaker than shank's fighters, that would be unrealistic imo. But having a smaller crew does mean that you must make up numbers for quality and strength, so I won't be surprised at all if Shanks commanders all have bounties higher than other yonko commanders and are a little bit more stronger than other yonko commanders.
The other thing I would like to add are the crew and commander compositions. Outside of blackbeard himself, the rest of the blackbeard pirates imo are a bit weak compared to the other yonko commanders, especially when you think how jesus burgess did against sabo, shiyu can be stronger than him, but I doubt he's ben Beckman level right now, same goes for yassop vs Van auger. Without blackbeard himself, I think the rest of his crew would lose against the other yonko commanders like katakuri, Beckman, or King. Kaido's Calamities seem pretty damn strong with their high bounties and their physical feats, but till now no one else outside the crew is really impressive save the Calamities, which are only 3 people. Kaido's crew so far have shown to have quantity but no quality. it's 3 Calamities vs Shanks top 3 + 5 other veterans. Headliners like Hawkins I don't count considering he didn't even defeat zoro. He could end up losing a arm just like Kidd. The whitebeard pirates would of have a better chance against the red hair pirates, but after losing Ace, Squatch and Jozu's arm I don't think they have the strength anymore, not to mention pops is also gone.
Realistically i actually think the big mom pirates are closest to the red hair pirates, quality and strength wise. Counting Snack, they have 4 sweet commanders, plus 3 and more veterans. Add in the large amounts of paramecia users in big mom's crew and the Red Hair pirates will be dealing with quite a handful.
So yeah I won't be surprised if on a crew to crew member basis the red hair pirates are the strongest individually, having more and stronger quality fighters, but I wouldn't go as far as to say they are 'twice' as strong as other yonko crews. That would be unrealistic, and if were true, would mean the other yonko commanders aren't up to scratch.