i haven't tried myself this plugin with 'cheetah sync', can't advise how to set up it, but if you have chosen 'resilio sync': 1st create somewhere (i've created inside 'music' folder) folder to keep links to music files, e.g. 'sync links', and set up plugin to use this folder. then open resilio sync on pc, and add 'sync links' folder to this app, click 'share' near the folder name, 'qr-code' tab, 'read and write' permission. open resilio sync on your phone, choose 'folders', tap '+' to add new folder. tap 'scan qr-code'. choose android folder to store synced files (i don't have sd card and don't know if it's allowed to choose sd card in resilio sync). disable 'selective sync', tap 'settings', disable 'use archive'. resilio sync on pc must be autostarted, but you must manually start it by default on your phone if you want to sync files, and i recommend keeping this default behavior.
p.s. by default plugin creates playlists on the phone with relative paths to music files, this should work fine.
p.p.s. you need android music played, which is capable either to add any folder containing music and playlists manually, or to auto-scan all folders on the phone. i'm using jetaudio+, it automatically finds all music and playlists on internal storage (i don't know if it can find music on sd card), and it perfectly reads .m3u playlists generated by 'sync links' plugin.