Rekordbox app iPhone

I want to start using rekordbox app on my iPhone
My iPhone has very low storage
My question is does my iPhone need lots of space to have all my tracks stored off rekordbox or is there an app I could use with it to store the tracks in like Dropbox so my phone doesn’t need all the songs on?

Also my xdj rx with rekordbox is very slow to show me way formd in performance mode and can’t keep up with the music that is playing in performance mode

Thanks