I’m curious how physics would affect the size and strength of human like aliens on super-earth worlds with 1 to 2 times the gravity of earth compared to humans. Would they be similar or be larger or smaller then humans based on the physics of their larger world? Would they need extra muscle mass to survive on super-earths?
Hypothetical aliens from super-earths would be dwarfs.
The forms of life under larger gravity will evolve smaller. The weight is proportional to the cube of the size, but the muscle strength is only proportional to the cross section area of the muscle, so the square of the size. Small animals are known to be relatively very strong for they weight: ants can lift loads up to 50 times they body weight (source) so potentially should be able to walk over much larger planet. And if they can walk, they probably can live there.
The aliens also need even large relative brain size than humans have, because while body can be smaller, it is not clear if the brain can be much smaller and still support the ability to think as humans do. It would be more evolutionary pressure against the growing brain, meaning that sentient life may have less chances to evolve.
Scaling gives some insights on this question.
The forces on the bones and muscles of a land animal will depend on its weight. Its weight is proportional to its volume times gravitational field, $g$. The volume goes as the cube of the linear size of the animal, $L$. So the forces go as $gL^3$. However, the strength of an animal's bones and muscles depends on their cross-section and tends to go only as the square of the linear size, $L^2$. The result is that big animals like elephants have disproprtionately thick legs.
Extending this analysis to varying the gravitational field we find that an elephant on a super earth with twice the gravitational field would be have to be half the linear size for its weight and strength to be correctly proportioned. So animals on a high-g plant might look quite similar but would generally be smaller versions. A half-size elephant (or a half-size human) could quite happily handle a 2g super-earth.
A half-size human would only have one-eighth the brain capacity. That seems a bit worrying. But brain size is not very closely related to intelligence. Sperm whales have brains five times bigger than human brains but we have trouble understanding how intelligent they are. Parrots manage remarkable feats of intelligence with brains one-hundredth the size of ours.