I'm working on a sci fi story where one of the species has batlike wings and comes from a moon around the size of Titan with roughly the same atmospheric pressure as Earth. Initially, I thought they'd be weaker than humans. But the idea originated from the fact that humans would be able to fly that way on Titan, presumably meaning that something that size able to fly on a world like that would at least have to be in the ballpark of human strength in order to fly there. So which would be more likely?
The exact comparison is difficult to make as it would depend on how the creatures used their wings. If they spent a lot of time soaring and gliding they might be able to get away with much less strength than creatures that had to climb and dive a lot to escape predators.
That said it is entirely reasonable to assume that the creatures and humans would be of roughly similar strength in some respects such as chest / arm muscles, but the creatures might also be seriously deficient in leg muscles.
One of the key adaptations for flight is lightness, particularly in bone structure. Weight, where needed, is optimised to support flight: even birds of prey don't have big muscly legs, for their killing impact they rely on sharp claws and beak. So your creatures, if human-sized, would be considerably less robust than a human, less able to carry heavy weights etc. but, if a carnivorous race, potentially still deadly owing to evolutionary adaptations such as claws, beaks.