Its most beneficial to use a shutter angle around 180 degrees for best looking motion blur. If you shoot in a 50Hz environment then its good to use 172 because that will reduce flicker around artificial light. This has no consequence underwater where you would use a dc light source.
Regarding kelvin I'd use a warm rather than cold setting so that you have some information in the red channel to work with when shooting without lights in prores (I recommend RAW for best results). That said I'd recommend you use a K that corresponds to your lights when using them and shoot raw when you are shooting without lights.
I shoot raw for WA and prores for macro with lights. I use a daylight setting for my kelvin when shooting prores.
Regarding the cards. There is still just one out there that supports RAW recording so the choice is kind of limited INMO.
Strangely enough, I have experienced flickering issues with powerful LED lights underwater, which could be corrected with an adjustment to shutterspeed. I experienced them at 1/50th sec with mangrove lights. It's not really a problem so long as you notice it underwater and correct it!