Hi,
I don't really shoot narrative film myself - my stuff is more landscape - but I'll try to help.
First, I actually made a review of the C80, which might help: https://moonblink.info/MudLake/gear#C80
Overall I think you'll find the C80 pretty easy to work with. You'll be focussing manually, of course, and your shutter speed and frame resolution will be set in advance for your project. Aperture will depend on your shot. So exposure is going to be mainly by ND filters - and you're going to love the built-in NDs on the C80. Having them in steps may seem like an issue, but they will always get you within 1 stop of the correct exposure, and if you need finer control than that, tweaking the ISO or aperture 1/3 of a stop won't be an issue.
Depending on how you plan to do focus, you might want to spend a little time (10 minutes) getting used to the focus aids on the C80 - peaking is useful, and the built-in focus guide works very well.
Likewise, spend a little more time getting used to the exposure aids - I find the waveform very helpful, but there's also false colour, which for narrative work might be better. ProAV recently did a whole video on false colour on the C80: https://www.youtube.com/watch?v=YpY7aaxYK5M
The base ISO is easy - I just set it to auto, and I think that works well. Most of the time I'm in bright light, and I just shoot ISO 800.
As for the codec to shoot - RAW ort whatever - I don't know if I can help much. I am shooting long-form stuff - I'm currently up to 28 hours of finished video - and I just shoot the most compressed mode, H.265 Long GOP, 135 Mb/s. Anything else and I would need to spend a lot more money on storage. But it's up to you. The extra bit depth of RAW might be an asset for VFX work, for example.
Personally I think people are generally way too much into pixel-peeping, and the compressed modes actually deliver great results. Bu you can judge for yourself: https://moonblink.info/MudLake/beauty
OK, I hope that helps, and have fun with the C80.
