Oda does not have to spell out that the 100 pirates were strong. Nitpicking about the exact amount of their bounties aside, logic dictates that the government would have been uimpressed had Law handed over a hodgepodge of high and low bounty pirates.
It is quite simple: Kid and his crew took a blast of Rayliegh's haki at the auction house and were still standing. That is no joke. He is at least comparable to Law and Luffy. Drake will also be quite powerful, we already know that he challenged a Yonko and is still alive, two years later. Kid has also challenged a Yonko and lived to tell. Both have been mentioned by name as having made a name for themselves in the New World. There should be know doubt both will be very important later on. Apoo, on the other hand, has already been chased off an island in the New World. By wild pigs. Not an auspicious start.
Otherwise we obviously know where Law stands. Hawkins brief post war appearance was impressive. Hard to say how strong he is but we know he can at least hold his own in the New World. Bonney was already defeated, the Capone Pirates appear to have been defeated. Killer will obviously be very strong, as part of Kid's crew. We obviously know where Zoro stands. The only Supernova who's strength is an unknown is Urouge. Not enough has been shown of him in the New World to predict success or failure.