Been meaning to test this for a while as Shane (biz partner) recently shot an Indie feature on the c300mkii (before external braw recording was enabled). Owning a G2 we wanted to check out the c300mkii (not 3) as a relatively inexpensive autofocus interview/gimbal camera to pair with the Ursa G2. It's certainly much smoother in the NLE keeping everything in BRAW rather than switching playback between codecs. But moving both cam's into gen5 (rather than staying in Clog2) really made life easier.
C300mkii footage recorded on Blackmagic Video Assist 7". I don't have a RED at the moment but I'd imagine recording raw out from the C300ii (and changing color space in post) would make it a far better RED autofocus B-cam too. Braw is super fast in Resolve, and plenty quick in Premiere too.