Thank you both for very thoughtful and helpful posts. They made additional questions occur to me.
I was surprised and relieved to learn that audio media may have folders, but how does the car stereo navigate them? I don't know if there's a standard for that, or it's a question that I'll have to ask in my car's owner forum.
Organizing my music according to "how I'll want to listen to it" is hard, because there's no one way. One day I may appreciate finding a track by searching for "flute"; another day I may appreciate finding the same track by searching for "Faure." Another day I might want to start with a search for "French Impressionist composers." I need some way to index the tracks according to multiple types of keys. I don't know if that's even possible in the car. I'm sure it can be done on a computer at home, but I don't know how, except by hand.
I can't speak for your player and it's navigation capability.
Any player should have "random" playback functionality of some type.
Speaking for mine...it's a Pioneer brand:
It CAN use folders, but it will NOT automatically move between them. That's a manual job.
I'd have to change folders manually via the controls and could easily get myself and others killed if done while the car is in motion due to distraction.
I could put all my Johnny Cash mp3s in a Johnny Cash folder and then play everything in that folder in either random order or in order by file name. If I then wanted to hear Henry Mancini or Elvis, I'd have to manually navigate to some other folder.
I occasionally have made multiple USB sticks by genre: one containing ONLY blues, all in a single folder. Another containing ONLY rockabilly, all in a single folder. Etc, switching sticks when I grew tired of a genre. But I gave up on that because I like genre-jumping at random. Muddy Waters followed by Gabby Pahinui followed by Hank Williams, all in one folder.
You could of course consider multiple sticks like "1940s" or "Instrumental only" or "Female Hawaiian vocalists". Or those folders on the same stick...may God help you with the navigation and search function.
I like random rather than non-random numerical or alphabetical because you get tired of hearing stuff in the same order. "I Walk The Line" is playing and you already know that "Folsom Prison Blues" is the next song. Maybe you are OK with that. I'm not. I love the element of surprise..."what's next??"
If not set to random order, a standard alphabetical sort order is used. The file names "Johnny Cash - I Walk The Line" would play AFTER "Dean Martin - I Walk The Line" and BEFORE "Timi Yuro - I Walk The Line".
I don't use numbers at the beginning of file names. They are unnecessary for my purposes. You MIGHT want to use numbers if you want to hear CDs or LPs in a specific order as released on the original CD. "01 Elvis - Hound Dog" should play BEFORE "02 Elvis - Don't Be Cruel".
I outright do not do any searching with my car player. It's doable but it's beyond tedious, entirely aside from the distraction danger. I don't tag by anything other than file name, artist, and song title. I don't need a machine to tell me that Elvis is in the rock and roll genre or that "Mystery Train" was recorded in 1955 and appeared on such and such CD.
If you asked me to play "Mystery Train" within 1 minute, I'd be dead in the water...but I don't mind that at all.
You could of course name folders "flute stuff" or "French impressionist stuff" as you see fit. You could even put the very same recording in more than one folder so that you might hear Herbie Mann in both "flute stuff" and "Jazz Instrumentals".
I've said "folders" throughout this. Fact is, I don't use folders at all. Everything is dumped into the root of the drive. 1800 songs. I hear music in random play from the root within 3 seconds of starting the car. If I turn off the ignition at 44 seconds into a song, that's where playback begins on the next start-up.
You'll likely have to compromise in car playback. Experiment and be prepared to change stuff around as you come to conclusions.