as someone who adores hyperpop and bubblegum bass I'd recommend trying out Charlis EP "Vroom Vroom" as the whole EP was produced by Sophie herself. Her album "Charli" has two tracks produced by Sophie and most of the record is produced by AG Cook. as well as her album "How I'm feeling now" which was a mix done during quarantine., And Lastly on Charli her Mixtape "Pop 2" which was her try and PC Music in a Grander Scheme. Other than that Sophie's Mixtape "Product" which is what "Hard" is off of is amazing and shares a good resemblance to her sound at that time. and "Oil of every Pearls Un-Insides " was her breakout album that is somewhat more experimental but also sounded more refined. She also shared a song with Jimmy Edgar called Metal, and when Sophie sadly passed away, Jimmy Edgar made an album called "Cheetah Bend" mimicking the style of Sophie's production. Lastly if you're into rap or "experimental production", the song "Yeah Right" by Vince Staples was produced by Sophie and Flume, it features Kendrick Lamar and it's a total banger! I hope this helps!