I figgered If a guy can install 4 matching modules in a 4 module board or 2 matching modules in a 2 module board, your system will be optimized into whatever “dual or quad-channel “ the board supports. Crucial.com has an index of max memory supported for most HP Dell Lenovo Sony Compaq etc..type pc’s.
I can't see any point in buying fast gaming memory. Crucial max is expensive and unless you're overclocking, probably not a good idea on a pc running 24/7 or an office pc designed with probably a marginal PSU, MB power stage and cooling, then why waste all that money? Standard memory will be fine. Faster timings or faster speeds are unlikely to yield any better results on something as low intensity as cctv. All you're doing is throwing money away unecessarily. XMP can be a good idea but XMP is unlikely to be supported on an office designed Motherboard. In any case, the speed increase is slight if noticeable. Again on something like BI, I doubt you'd notice it. It certainly isn't worth the extra expense of a gaming pc.
Just looking at the Crucial memory selector site, you can buy a kit for the HP G5 400 consisting of 16gb of dual channel memory (2x8gb) 2666mhz for £56. That's about 1/4 the cost of Crucial Max ddr4000 which is only going to run at the standard pc speed anyway, of 2666 unless the system is overclocked, which isn't advisable for the reasons given before. My advice would be save your money. If the pc comes with 16gb, then leave it. If it doesn't and you want 16gb, get the cheap Crucial kit or similr. Don't waste your money buying Ferrari memory for a Jalopy. Putting a Ferrari steering wheel in a jalopy motor doesn't make it go any faster!