I have no problem with the characters you indicate whether with my Prime GO or Prime 4 and yet I have a lot of music with different special characters. The only problem that arises is during a search in the player or the software where it will be necessary to write the title and the artist correctly, if they contain any.
I don’t know, if you are talking about this kind of problem or not?
https://community.enginedj.com/t/red-tracks-on-sd-card-or-usb-after-using-sync-manager/42794/12
As for the HFS+ format, I couldn’t help you because all my SSD or SD card and USB key are in Exfat format, which allows me to access the content of the media on any machine (PC/Mac)