In the Thor Love & Thunder film, Jane (Natalie Portman), correct me if I'm wrong, was terminally ill with cancer. But with "broken" Mjolnir she transformed to a fit Mighty Thor herself with accompanying Thor-like costume, while Steve did not back in Endgame. Or perhaps because Steve purposefully didn't need or want to back then.
So wouldn't it be similar with old Steve. Imagine him temporarily transforming to a fit Cap again as any dire, desperate situation, Avenger-level event would call for. He could easily make an educated wish to grant him a more classic scale-armored Captain America with side "wings", which could be designed enough to make it more Norse/Thor-like too yet still very much Cap. Which would also differentiate to Sam's own present Cap incarnation.
Now, I might as well. Regarding Jane if she was "worthy" back in L&T, I theorize she wasn't initially. But since Thor inadvertently put a spell or similar to Mjolnir when he asked it to protect Jane, the hammer responded to her when the time came to do it, which was when she was sick and she went near it in the movie. It restored her to full health with bigger physique too, although only temporarily.
Odin's old enchantment is always there, which is "if he be worthy", and NOT "if he be NOT worthy". So if worthy, then the hammer will respond. Then if it is Jane, then it will also respond. But if Odin's enchantment was something like "if he be NOT worthy, he would NOT possess the powers of Thor", then if Jane was indeed not worthy initially, then the two would simply cancel each other out. Equally, perfectly balanced like all things should be.
So at least seemingly two rules the hammer will follow or respond to. Then later, Thor talked to Jane that she was worthy.
Re Jane, I don't think it's matter of being worthy. The specific rule applies over the more general rule. The protection of Jane is also an ambiguous one. Hypothetically if Jane were under attack by aliens Mjolnir might have just flew in and defeated the aliens, not transforming Jane.
In terms of Jane actually being worthy, we don't see her a lot in the films. I think the sacrifice she makes at the end of Love and Thunder proves that she is capable of being worthy. However similar to Cap not being able to lift it fully in Age of Ultron I suspect Jane would also be unable to lift it. Of course Mjolnir and Jane (and Thor) spent a lot of time together, so she may be able.