WD Blue SA510

The biggest performance upgrade IMO is replacing the HDD with a SSD. Watch out for cheap SSDs though, they likely will not have a DRAM cache, the unbranded or obscure branded ones particulary. Personally I'd always go for a known performance brand with a DRAM cache, e.g. Samsung 870 EVO or WD Blue S

The 2TB SA510 uses a different(better) controller and is a better drive than the lower capacity SA510 drives. The lower capacities uses a WD controller that was pretty bad. WD literally used the controller on just the WD Blue SSDs and then abandoned it...I wonder why... The 2TB version uses a Silico

For sata ssds, they are all basically the same. The only real difference you will come across is if it has dram (technically better) or not. The 870 has dram, I went with one with dram (WD Blue SA510). At max throughout with 16 cameras you're only looking at about 64 mb/s. Well under the max through