I think it would be super varied! Legend is deeply musical and probably has fairly diverse listening habits beyond his general, preferential tastes, and Hyrule might be a little out of touch with current hits beyond whatever plays in the hospital's common areas or on TV, but he's from a different country with its own artists and his base tastes and listening habits reflect that.
If they have a trip coming up, Legend creates a playlist for them to both add to and gets a head-start on it by at least a month, so Hyrule has plenty of time to contribute, and he tries to keep things super even so Hyrule's selections aren't overwhelmed by his. The only criteria is that the playlist is long enough to cover the trip completely in one direction, without repeats, so it gets listened to in full twice per roadtrip.
They can go from pop-punk they both remember from their teens and can still sing along to, to Bad Blupee, to Akkala Highlands trad, to Rob Redead, to moody blues, to Calatian dance hall, to classical concertos, to Run LOZ, to obscure Zora jazz, to bedroom pop, to queer punk, to cello solos, to 80s goth club bangers and weird alt shit, to Ordon folk and bluegrass, to industrial, to modern composers and experimental pieces, to the occasional showtune, to covers of other songs they know, to clever send-ups of older styles like "I've No More Fucks to Give," to trap, to whatever Top 40 schlock "hits" are the hardest to escape, to viral social media artists. Legend will focus on what he's been listening to recently and will also throw things he's never really listened to before in, like things that are sampled as audio on social media, too.
Hyrule has put embargoes on anything "too fast" (so no hyperpop, but he'll tolerate some dubstep or house music) or "too screamy" (so none of several metal genres), opera and/or other technical vocal work like throat singing or what we would consider Nordic or Viking metal), or really, really out there experimental noise. He also doesn't understand the appeal of mumblerap and "really talky" storytellers (he's not a fan of narrative music, broadly speaking, so Bob Moblin is a no-go). Legend will tolerate a lot, but he does get bored by low-fi and overstimulated by certain types of traditional Calatian brass-heavy folk if too much of either keeps coming up on the shuffle in quick succession, and he just doesn't like overly produced music of all genres beyond indie artists who self-produce (so no bubblegum/boyband/supergroup pop, and no drag artists or gay house music). Neither of them are into divas.
If any of the other boys are accidentally added to the playlist, depending on the respective boy and his restraint, a joke song like "Enormous Penis," "No Cock Like Horse Cock," or "Red Flags" (better known as the Human Centipede song by Tom Cardy) is almost guaranteed to end up in the mix.
