Late, but better late than never, I guess..
I just found a mod on NexusMods yesterday that removes the sharpening and (optionally) film grain without any graphical side effects: https://www.nexusmods.com/needforspeedheat/mods/55
I'm so glad I found that, the game looks much better without the sharpening! Personally I don't mind the film grain after the sharpening is gone; it's rather subtle, at least on 1440p, and can help with some bland looking situations in the game. But luckily you have the freedom to remove both. 🙂
Hope this info helps someone and spreads the word of this great mod.