Will I lose Mail folders or iTunes playlists if I reinstall Mojave?

I am having multiple issues with my iMac and it has been suggested in conversations with Apple that I reinstall the OS. I did not ask at the time if I will lose my Mail folders and/or my iTunes playlists. I assume programs and data will remain (but I backup using Backblaze so I am prepared if I lose anything), but it has occurred to me that programs installed as part of the OS may not save preferences. So I'm wondering what I may lose in the reinstall even if it goes perfectly. And if I lose something like folders and Mail rules, is there a way to get them back without having to recreate them all?