mbzn

I have kodak fl5.2's on my og7.2 working flawless. I believe they use the same bms as the pylontech. I would not hesitate to go kodak again although i have zero experience with pylontech.

As for the switch(I'm not an electrician nor do i have all the sans codes) but it seems the sans 164-1 plugs was the main issue as there was a possibility to touch the terminals while being unplugged. They are sort of phased out. The newer ones 'sans 164-2' has this sorted so the plug is already disconnected before the live terminal is exposed.
My guess is 164-1 needs an isolator whereas 164-2 dont. I might be wrong though, so better let an informed sparky answer to this.
As for the dc, even wired cameras has dc wires to them and i dont think it's covered by coc, afaik because you can unplug the power supply it's not considered part of the site's wireing, also 12v dc is not considered dangerous to a person.
Again, please confirm with an qualified electrician before installing solely on my limited knowledge.

Your batteries might take you further than you expect. Thats 14 units of eskom in there. Cut the high loads during the night and you'll pretty much be set. After a few week you'll know where you're short and can invest accordingly.