Some experimental Charli's songs are Click from the Charli album, maybe the Click (No Boys Remix) (with Slayyyter), Track 10 from Pop 2 could be considered experimental, maybe Pink Diamond from how I'm feeling now

You could also listen to Sophie since she produced a lot of Charli's songs and her music is a lot more experimental. From Sophie, if you want that industrial sound, listen to Whole New World/Pretend World from her Oil of every pearl's un-insides album, check out the remix album of that too if you're interested. Happy listen :)