It really depends on the source of the super strength. The juggernaut is a god-empowered being of strength; he looks muscley because that’s what strength is supposed to look like, not because it affects his ability to do work.

Superman looks strong because that’s the ideal humanoid form, apparently, and his eugenics-obsessed ancestors chose that as the look they wanted to breed for.

Mr incredible/robert parr from the incredibles had to work out, and used literal trains as his gym equipement. It’s likely his super power wasn’t super strength so much as fewer limits on how much improvement he could get from his workouts. He is out of shape at the start of his story, and getting rid of that, while relatively easy for him compared to others, did require actual work on his part.

If you had a superhero who had like, a psychic shield or similar that surrounded their body and gave the appearance of super strength, like Victoria Dallon from Worm, then yeah, they’d have to work a lot harder to look like the strength they use on a regular basis.

Except in rare cases, I think you’ve got it backwards. Heroes with super strength get their muscles from their powers, and only the rare few outliers don’t get muscles from their superpowers.