I always encourage up and coming rappers to start of rapping over freestyle beats as it’s much easier for you to follow the snare. The tempo of freestyle rap beats tends to be commonly found between 85 - 95 BPM.
Freestyle instrumentals are much more simplistic. Consisting of a basic boom-bap drum pattern. Using a combination of the Kick, The Snare and High Hats and some light percussive instruments.
These old school instrumentals are based on old jazz samples. The pioneers of freestyle beats included producers like DJ Premier, 9th Wonder and Jay Dilla.
All of the producers would create a simple boom bap beat and add chopped up samples obtained from old soul records.
Freestyle beats have much more room in them for the rapper to shine. There is less distraction from the instrumentation to distract the rapper.
Compared to most modern trap beat which sometimes steals the limelight form the rap artist.
Trap beats are more suited for clubs and live shows.
Designed to hype the audience.
Freestyle beats, on the other hand, are more suited to rappers that want their lyrics to shine. If you have an important story to tell or you feel that the lyrics that you have written deserve to be heard then freestyle instrumentals are the best place to start.