I have used the Tiffen Black Pro Mist filters but decided to get my hands on the K&F Concept Nano-X Pro MRC Black Mist diffusion filters too and don't regret my decision at all.
They're really well made and cheaper than the Tiffen which is regarded as the best.
I usually have the 1/8 on my lens and only bring the 1/4 for cinematic b-roll.
It take more than a diffusion filter to make your scenes look "cinematic" but it's a cheap and easy way to start.
Camera: Blackmagic Pocket Cinema Camera Pocket 6k Pro
Lens: Sigma 18-35 mm f/1.8
Shot in BRAW 8:1 6K