It's changed over time. Originally, it was just that the Kryptonians had evolved to the peak of perfection and thus they all had superpowers. (In the radio pilot episode, Jor-El had to explain to an astonished Lara that Earthlings couldn't travel clear across town in a single step but could only stride a few feet at a time.) Then the high-gravity thing was established as the reason Superman had superstrength on Earth (basically John Carter of Mars in reverse). The yellow-sun thing didn't come along until the Silver Age, the '50s or '60s, although they kept the high gravity too.
Of course, every adaptation is its own separate reality, and can do whatever it wants with the question of Krypton's gravity. I'd say it's fairly typical for screen productions to portray Krypton's gravity as comparable to Earth's. Supergirl had humans able to move normally on Fort Rozz, a Kryptonian-built space station whose onboard gravity was presumably calibrated to Krypton level. I believe Lois & Clark did the equivalent with the Kryptonian starship that appeared in the later seasons.
