We had an FS700: +1 on ETTR and while I would not use Slog(x) for internal recording, it's fine if recording RAW to ProRes (10-bit). If after grading and compressing for final delivery (e.g. online streaming means at least 1 H.264 pass) the noise is too much, Neat Video is your best option (only after done with everything else- it slows down the workflow; no point even messing with it (other than a quick test to make sure the clips are usable after NR)). One of the secrets of the A7S I/II is the in-camera NR (probably more than the hardware).
The FS700 is decent in lowlight, however slomo and super slomo needs a lot of light, else it's noisy, e.g. 240fps = 1/240 - 1/480 shutter.
I have FS5 which said to be better performance than FS700 but lowlight still outgunned by much cheaper A6300, FS700 can only be worse, I guess their good low light performance is for year 2012 and not year 2017
Lewis Hart reacted to jcs in Horrific noise from FS700 both in 4K & 1080 Slowmo